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Engineering S. oneidensis for Performance Improvement of Microbial Fuel Cell-a Mini Review

Leung DHL, Lim YS, Uma K, Pan GT, Lin JH, Chong S, et al.

Appl Biochem Biotechnol, 2021 Apr;193(4):1170-1186.
PMID: 33200267 DOI: 10.1007/s12010-020-03469-6

Microbial fuel cell (MFC) is a promising technology that utilizes exoelectrogens cultivated in the form of biofilm to generate power from various types of sources supplied. A metal-reducing pathway is utilized by these organisms to transfer electrons obtained from the metabolism of substrate from anaerobic respiration extracellularly. A widely established model organism that is capable of extracellular electron transfer (EET) is Shewanella oneidensis. This review highlights the strategies used in the transformation of S. oneidensis and the recent development of MFC in terms of intervention through genetic modifications. S. oneidensis was genetically engineered for several aims including the study on the underlying mechanisms of EET, and the enhancement of power generation and wastewater treating potential when used in an MFC. Through engineering S. oneidensis, genes responsible for EET are identified and strategies on enhancing the EET efficiency are studied. Overexpressing genes related to EET to enhance biofilm formation, mediator biosynthesis, and respiration appears as one of the common approaches.

Matched MeSH terms: Biofilms/growth & development*
Fulltext Potential of Superhydrophobic Surface for Blood-Contacting Medical Devices

Wu XH, Liew YK, Mai CW, Then YY

Int J Mol Sci, 2021 Mar 24;22(7).
PMID: 33805207 DOI: 10.3390/ijms22073341

Medical devices are indispensable in the healthcare setting, ranging from diagnostic tools to therapeutic instruments, and even supporting equipment. However, these medical devices may be associated with life-threatening complications when exposed to blood. To date, medical device-related infections have been a major drawback causing high mortality. Device-induced hemolysis, albeit often neglected, results in negative impacts, including thrombotic events. Various strategies have been approached to overcome these issues, but the outcomes are yet to be considered as successful. Recently, superhydrophobic materials or coatings have been brought to attention in various fields. Superhydrophobic surfaces are proposed to be ideal blood-compatible biomaterials attributed to their beneficial characteristics. Reports have substantiated the blood repellence of a superhydrophobic surface, which helps to prevent damage on blood cells upon cell-surface interaction, thereby alleviating subsequent complications. The anti-biofouling effect of superhydrophobic surfaces is also desired in medical devices as it resists the adhesion of organic substances, such as blood cells and microorganisms. In this review, we will focus on the discussion about the potential contribution of superhydrophobic surfaces on enhancing the hemocompatibility of blood-contacting medical devices.

Matched MeSH terms: Biofilms/drug effects
Fulltext Quaternary ammonium silane (k21) based intracanal medicament triggers biofilm destruction

Kok ESK, Lim XJ, Chew SX, Ong SF, See LY, Lim SH, et al.

BMC Oral Health, 2021 03 12;21(1):116.
PMID: 33711992 DOI: 10.1186/s12903-021-01470-x

BACKGROUND: Compare antimicrobial efficacy of a quarternary ammonium silane (QAS)/k21 as an intracanal medicament against E. faecalis and C. albicans biofilms formed on root dentin.
METHODOLOGY: Dentin blocks were sterilized and E. faecalis and C. albicans microbial colonies were counted for colony-forming-units against 2%k21, 2%CHX and Ca(OH)2 medicaments. Biofilm colonies after 7 days on dentin were analysed using confocal laser scanning microscopy with live/dead bacterial viability staining. TEM was done to study dentin collagen matrix. Dentin discs from 3rd day and 7th day well plate was used for Raman spectra and observed under fluorescent-microscope. Docking studies were carried out on MMP-2 S1 binding-domain with k21.
RESULTS: There was reduction of E. faecalis/C. albicans when k21, chlorhexidine and calcium hydroxide were used with highest percentage in 2%k21 treated specimens. 2%k21 showed dense and regular collagen network with intact cross-banding and decreased Raman intensity for 2%k21 on 3rd day. NaOCl + k21 showed least adherence, whereas saline groups showed highest adherence of E. faecalis and C. albicans to root-canal dentin. Alizarin red staining of hDPSCs revealed calcium deposition in all groups with significant difference seen amongst 2%k21 groups. MMP-2 ligand binding was seen accurately indicating possible target sites for k21 intervention.
CONCLUSION: 2%k21 can be considered as alternative intracanal medicament.

Matched MeSH terms: Biofilms
Surface engineered iron oxide nanoparticles as efficient materials for antibiofilm application

Velusamy P, Su CH, Kannan K, Kumar GV, Anbu P, Gopinath SCB

Biotechnol Appl Biochem, 2021 Mar 10.
PMID: 33751641 DOI: 10.1002/bab.2146

Overuse of antibiotics has led to the development of multi drug resistant strains. Antibiotic resistance is a major drawback in the biomedical field since medical implants are prone to infection by biofilms of antibiotic resistant strains of bacteria. With increasing prevalence of antibiotic resistant pathogenic bacteria, the search for alternative method is utmost importance. In this regard, magnetic nanoparticles are commonly used as a substitute for antibiotics that can circumvent the problem of biofilms growth on the surface of biomedical implants. Iron oxide nanoparticles (IONPs) have unique magnetic properties that can be exploited in various ways in the biomedical applications. IONPs are engineered employing different methods to induce surface functionalization that include the use of polyethyleneimine and oleic acid. IONPs have a mechanical effect on biofilms when in presence of an external magnet. In this review, a detailed description of surface engineered magnetic nanoparticles as ideal antibacterial agents is provided, accompanied by various methods of literature review. This article is protected by copyright. All rights reserved.

Matched MeSH terms: Biofilms
LC-MS analysis reveals biological and metabolic processes essential for Candida albicans biofilm growth

Munusamy K, Loke MF, Vadivelu J, Tay ST

Microb Pathog, 2021 Mar;152:104614.
PMID: 33202254 DOI: 10.1016/j.micpath.2020.104614

Candidiasis is the most common fungal infection associated with high morbidity and mortality among immunocompromised patients. The ability to form biofilm is essential for Candida albicans pathogenesis and drug resistance. In this study, the planktonic cell and biofilm proteomes of C. albicans SC5314 strain analyzed using Liquid Chromatography-Mass Spectrometry (LC-MS) were compared. In total, 280 and 449 proteins are annotated from the planktonic cell and biofilm proteomes, respectively. The biofilm proteome demonstrated significantly higher proportion of proteins associated with the endomembrane system, mitochondrion and cytoplasm than planktonic proteome. Among proteins detected, 143 and 207 biological processes are annotated, of which, 38 and 102 are specific to the planktonic cell and biofilm proteomes, respectively, while 105 are common biological processes. The specific biological processes of C. albicans planktonic cell proteome are associated with cell polarity, energy metabolism and nucleotide (purine) metabolism, oxido-reduction coenzyme metabolic process, monosaccharide and amino acid (methionine) biosynthesis, regulation of anatomical structure morphogenesis and cell cycling, and single organism reproduction. Meanwhile, regulation of cellular macromolecule biosynthesis and metabolism, transcription and gene expression are major biological processes specifically associated with C. albicans biofilm proteome. Biosynthesis of leucine, isoleucine, and thiocysteine are highlighted as planktonic-related pathways, whereas folate metabolism, fatty acid metabolism and biosynthesis of amino acids (lysine, serine and glycine) are highlighted as biofilm-related pathways. In summary, LC-MS-based proteomic analysis reveals different adaptative strategies of C. albicans via specific biological and metabolic processes for planktonic cell and biofilm lifestyles. The mass spectrometry data are available via ProteomeXchange with identifiers PXD007830 (for biofilm proteome) and PXD007831 (for planktonic cell proteome).

Matched MeSH terms: Biofilms
Formulation of a Semisolid Emulsion Containing Leptospermum scoparium Essential Oil and Evaluation of In Vitro Antimicrobial and Antibiofilm Efficacy

Porter GC, Safii SH, Medlicott NJ, Duncan WJ, Tompkins GR, Coates DE

Planta Med, 2021 Mar;87(3):253-266.
PMID: 33434939 DOI: 10.1055/a-1330-8765

Manuka oil, an essential oil derived from the Leptospermum scoparium, has been traditionally used for wound care and as a topical antibacterial, antifungal, and anti-inflammatory. However, the essential oil is not well retained at mucosal sites, such as the oral cavity, where the benefits of the aforementioned properties could be utilized toward the treatment of persistent biofilms. Within this study, L. scoparium essential oil was incorporated into a semisolid emulsion for improved delivery. The safety profile of L. scoparium essential oil on human gingival fibroblasts was determined via cell viability, cytotoxicity, and caspase activation. The minimal bactericidal concentration of L. scoparium essential oil was determined, and the emulsion's antibiofilm effects visualized using confocal laser scanning microscopy. L. scoparium essential oil demonstrated a lower IC50 (0.02% at 48 h) when compared to the clinical control chlorhexidine (0.002% at 48 h) and displayed lower cumulative cytotoxicity. Higher concentrations of L. scoparium essential oil (≥ 0.1%) at 6 h resulted in higher caspase 3/7 activation, suggesting an apoptotic pathway of cell death. A minimal bactericidal concentration of 0.1% w/w was observed for 6 oral bacteria and 0.01% w/v for Porphyromonas gingivalis. Textural and rheometric analysis indicated increased stability of emulsion with a 1 : 3 ratio of L. scoparium essential oil: Oryza sativa carrier oil. The optimized 5% w/w L. scoparium essential oil emulsion showed increased bactericidal penetrative effects on Streptococci gordonii biofilms compared to oil alone and to chlorhexidine controls. This study has demonstrated the safety, formulation, and antimicrobial activity of L. scoparium essential oil emulsion for potential antibacterial applications at mucosal sites.

Matched MeSH terms: Biofilms
Fulltext Application of Zwitterions in Forward Osmosis: A Short Review

Chiao YH, Sengupta A, Ang MBMY, Chen ST, Haan TY, Almodovar J, et al.

Polymers (Basel), 2021 Feb 15;13(4).
PMID: 33672026 DOI: 10.3390/polym13040583

Forward osmosis (FO) is an important desalination method to produce potable water. It was also used to treat different wastewater streams, including industrial as well as municipal wastewater. Though FO is environmentally benign, energy intensive, and highly efficient; it still suffers from four types of fouling namely: organic fouling, inorganic scaling, biofouling and colloidal fouling or a combination of these types of fouling. Membrane fouling may require simple shear force and physical cleaning for sufficient recovery of membrane performance. Severe fouling may need chemical cleaning, especially when a slimy biofilm or severe microbial colony is formed. Modification of FO membrane through introducing zwitterionic moieties on the membrane surface has been proven to enhance antifouling property. In addition, it could also significantly improve the separation efficiency and longevity of the membrane. Zwitterion moieties can also incorporate in draw solution as electrolytes in FO process. It could be in a form of a monomer or a polymer. Hence, this review comprehensively discussed several methods of inclusion of zwitterionic moieties in FO membrane. These methods include atom transfer radical polymerization (ATRP); second interfacial polymerization (SIP); coating and in situ formation. Furthermore, an attempt was made to understand the mechanism of improvement in FO performance by zwitterionic moieties. Finally, the future prospective of the application of zwitterions in FO has been discussed.

Matched MeSH terms: Biofilms
The antimicrobial and antibiofilm properties of allicin against Candida albicans and Staphylococcus aureus - A therapeutic potential for denture stomatitis

Zainal M, Mohamad Zain N, Mohd Amin I, Ahmad VN

Saudi Dent J, 2021 Feb;33(2):105-111.
PMID: 33551624 DOI: 10.1016/j.sdentj.2020.01.008

The objective of this study is to determine the therapeutic efficacy of allicin against Candida albicans (C. albicans) and Staphylococcus aureus (S. aureus), the common etiological agents for denture stomatitis (DS). The minimum inhibitory concentration (MICs), minimum bactericidal concentrations (MBCs) and minimum fungicidal concentration (MFCs) of allicin were determined by the broth microdilution method followed by checkerboard microdilution method for a synergistic interaction between allicin + nystatin and allicin + CHX. The potential of allicin to eradicate C. albicans and S. aureus biofilms was assessed by treating biofilm formed on self- polymerized acrylic resin with allicin at a sub-MIC concentration for 5 min. The commercial denture cleanser (brand X) was used as a positive control. A Kruskal-Wallis test followed by the post-hoc Mann-Whitney U test was applied (SPSS 20.0), and the level of significance was set at P

Matched MeSH terms: Biofilms
Efflux pump inhibitors: new updates

AlMatar M, Albarri O, Makky EA, Köksal F

Pharmacol Rep, 2021 Feb;73(1):1-16.
PMID: 32946075 DOI: 10.1007/s43440-020-00160-9

The discovery of antibiotics ought to have ended the issue of bacterial infections, but this was not the case as it has led to the evolution of various mechanisms of bacterial resistance against various antibiotics. The efflux pump remains one of the mechanisms through which organisms develop resistance against antibiotics; this is because organisms can extrude most of the clinically relevant antibiotics from the interior cell environment to the exterior environment via the efflux pumps. Efflux pumps are thought to contribute significantly to biofilm formation as highlighted by various studies. Therefore, the inhibition of these efflux pumps can be a potential way of improving the activity of antibiotics, particularly now that the discovery of novel antibiotics is becoming tedious. Efflux pump inhibitors (EPIs) are molecules that can inhibit efflux pumps; they have been considered potential therapeutic agents for rejuvenating the activity of antibiotics that have already lost their activity against bacteria. However, studies are yet to determine the specific substrates for such pumps; the effect of altered efflux activity of these pumps on biofilm formation is still being investigated. A clear knowledge of the involvement of efflux pumps in biofilm development could aid in developing new agents that can interfere with their function and help to prevent biofilms formation; thereby, improving the outcome of treatment strategies. This review focuses on the novel update of EPIs and discusses the evidence of the roles of efflux pumps in biofilm formation; the potential approaches towards overcoming the increasing problem of biofilm-based infections are also discussed.

Matched MeSH terms: Biofilms/drug effects
Fulltext Effect of Propolis Nanoparticles against Enterococcus faecalis Biofilm in the Root Canal

Parolia A, Kumar H, Ramamurthy S, Madheswaran T, Davamani F, Pichika MR, et al.

Molecules, 2021 Jan 30;26(3).
PMID: 33573147 DOI: 10.3390/molecules26030715

To determine the antibacterial effect of propolis nanoparticles (PNs) as an endodontic irrigant against Enterococcus faecalis biofilm inside the endodontic root canal system. Two-hundred-ten extracted human teeth were sectioned to obtain 6 mm of the middle third of the root. The root canal was enlarged to an internal diameter of 0.9 mm. The specimens were inoculated with E. faecalis for 21 days. Following this, specimens were randomly divided into seven groups, with 30 dentinal blocks in each group including: group I-saline; group II-propolis 100 µg/mL; group III-propolis 300 µg/mL; group IV-propolis nanoparticle 100 µg/mL; group V-propolis nanoparticle 300µg/mL; group VI-6% sodium hypochlorite; group VII-2% chlorhexidine. Dentin shavings were collected at 200 and 400 μm depths, and total numbers of CFUs were determined at the end of one, five, and ten minutes. The non-parametric Kruskal-Wallis and Mann-Whitney tests were used to compare the differences in reduction in CFUs between all groups, and probability values of p < 0.05 were set as the reference for statistically significant results. The antibacterial effect of PNs as an endodontic irrigant was also assessed against E. faecalis isolates from patients with failed root canal treatment. Scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) were also performed after exposure to PNs. A Raman spectroscope, equipped with a Leica microscope and lenses with curve-fitting Raman software, was used for analysis. The molecular interactions between bioactive compounds of propolis (Pinocembrin, Kaempferol, and Quercetin) and the proteins Sortase A and β-galactosidase were also understood by computational molecular docking studies. PN300 was significantly more effective in reducing CFUs compared to all other groups (p < 0.05) except 6% NaOCl and 2% CHX (p > 0.05) at all time intervals and both depths. At five minutes, 6% NaOCl and 2% CHX were the most effective in reducing CFUs (p < 0.05). However, no significant difference was found between PN300, 6% NaOCl, and 2% CHX at 10 min (p > 0.05). SEM images also showed the maximum reduction in E. faecalis with PN300, 6% NaOCl, and 2% CHX at five and ten minutes. CLSM images showed the number of dead cells in dentin were highest with PN300 compared to PN100 and saline. There was a reduction in the 484 cm-1 band and an increase in the 870 cm-1 band in the PN300 group. The detailed observations of the docking poses of bioactive compounds and their interactions with key residues of the binding site in all the three docking protocols revealed that the interactions were consistent with reasonable docking and IFD docking scores. PN300 was equally as effective as 6% NaOCl and 2% CHX in reducing the E. faecalis biofilms.

Matched MeSH terms: Biofilms/drug effects
Fulltext Morphological, Structural, Thermal, Permeability, and Antimicrobial Activity of PBS and PBS/TPS Films Incorporated with Biomaster-Silver for Food Packaging Application

Aziman N, Kian LK, Jawaid M, Sanny M, Alamery S

Polymers (Basel), 2021 Jan 27;13(3).
PMID: 33513665 DOI: 10.3390/polym13030391

The development of antimicrobial film for food packaging application had become the focus for researchers and scientists. This research aims to study the characteristics and antimicrobial activity of novel biofilms made of poly (butylene succinate) (PBS) and tapioca starch (TPS) added with 1.5% or 3% of Biomaster-silver (BM) particle. In morphological examination, the incorporation of 3% BM particle was considerably good in forming well-structured PBS film. Meanwhile, the functional groups analysis revealed the 3% BM particle was effectively interacted with PBS molecular chains. The flame retard behavior of BM metal particle also helped in enhancing the thermal stability for pure PBS and PBS/TPS films. The nucleating effect of BM particles had improved the films crystallinity. Small pore size features with high barrier property for gas permeability was obtained for BM filled PBS/TPS films. From antimicrobial analysis, the BM particles possessed antimicrobial activity against three bacteria Staphylococcus aureus, Escherichia coli, and Salmonella Typhimurium in which PBS/TPS 3% BM film exhibited strong antimicrobial activity against all tested bacteria, however, PBS/TPS 1.5% BM film exhibited strong antimicrobial activity against E. coli only. Hence, the incorporation of BM into PBS/TPS film could be a sustainable way for developing packaging films to preserve food products.

Matched MeSH terms: Biofilms
Betacyanin-inhibited biofilm formation of co-culture of Staphylococcus aureus and Pseudomonas aeruginosa on different polymer surfaces

Yong YY, Ong MWK, Dykes G, Choo WS

FEMS Microbiol Lett, 2021 01 26;368(1).
PMID: 33338235 DOI: 10.1093/femsle/fnaa214

Staphylococcus aureus and Pseudomonas aeruginosa are bacteria that cause biofilm-associated infections. The aim of this study was to determine the activity of combined betacyanin fractions from Amaranthus dubius (red spinach) and Hylocereus polyrhizus (red pitahaya) against biofilms formed by co-culture of S. aureus and P. aeruginosa on different polymer surfaces. Various formulations containing different concentrations of the betacyanin fractions were investigated for biofilm-inhibiting activity on polystyrene surfaces using crystal violet assay and scanning electron microscopy. A combination of each betacyanin fraction (0.625 mg mL-1) reduced biofilm formation of five S. aureus strains and four P. aeruginosa strains from optical density values of 1.24-3.84 and 1.25-3.52 to 0.81-2.63 and 0.80-1.71, respectively. These combined fractions also significantly inhibited dual-species biofilms by 2.30 and reduced 1.0-1.3 log CFU cm-2 bacterial attachment on polymer surfaces such as polyvinyl chloride, polyethylene, polypropylene and silicone rubber. This study demonstrated an increase in biofilm-inhibiting activity against biofilms formed by two species using combined fractions than that by using single fractions. Betacyanins found in different plants could collectively be used to potentially decrease the risk of biofilm-associated infections caused by these bacteria on hydrophobic polymers.

Matched MeSH terms: Biofilms/drug effects*
Fulltext Transcriptome Analysis of Pseudomonas aeruginosa Biofilm Following the Exposure to Malaysian Stingless Bee Honey

Seder N, Abu Bakar MH, Abu Rayyan WS

Adv Appl Bioinform Chem, 2021;14:1-11.
PMID: 33488102 DOI: 10.2147/AABC.S292143

Introduction: Malaysian stingless bee honey (Trigona) has been aroused as a potential antimicrobial compound with antibiofilm activity. The capability of the gram-negative bacillus P. aeruginosa to sustain a fatal infection is encoded in the bacterium genome.
Methods: In the current study, a transcriptome investigation was performed to explore the mechanism underlying the biofilm dispersal of P. aeruginosa after the exposure to Trigona honey.
Results: Microarray analysis of the Pseudomonas biofilm treated by 20% Trigona honey has revealed a down-regulation of 3478 genes among the 6085 screened genes. Specifically, around 13.5% of the down-regulated genes were biofilm-associated genes. The mapping of the biofilm-associated pathways has shown an ultimate decrease in the expression levels of the D-GMP signaling pathway and diguanylate cyclases (DGCs) genes responsible for c-di-GMP formation.
Conclusion: We predominantly report the lowering of c-di-GMP through the down-regulation of DGC genes as the main mechanism of biofilm inhibition by Trigona honey.

Matched MeSH terms: Biofilms
Fulltext Amylases: Biofilm Inducer or Biofilm Inhibitor?

Lahiri D, Nag M, Banerjee R, Mukherjee D, Garai S, Sarkar T, et al.

Front Cell Infect Microbiol, 2021;11:660048.
PMID: 33987107 DOI: 10.3389/fcimb.2021.660048

Biofilm is a syntrophic association of sessile groups of microbial cells that adhere to biotic and abiotic surfaces with the help of pili and extracellular polymeric substances (EPS). EPSs also prevent penetration of antimicrobials/antibiotics into the sessile groups of cells. Hence, methods and agents to avoid or remove biofilms are urgently needed. Enzymes play important roles in the removal of biofilm in natural environments and may be promising agents for this purpose. As the major component of the EPS is polysaccharide, amylase has inhibited EPS by preventing the adherence of the microbial cells, thus making amylase a suitable antimicrobial agent. On the other hand, salivary amylase binds to amylase-binding protein of plaque-forming Streptococci and initiates the formation of biofilm. This review investigates the contradictory actions and microbe-associated genes of amylases, with emphasis on their structural and functional characteristics.

Matched MeSH terms: Biofilms*
Fulltext Prodigiosin inhibits bacterial growth and virulence factors as a potential physiological response to interspecies competition

Yip CH, Mahalingam S, Wan KL, Nathan S

PLoS One, 2021;16(6):e0253445.
PMID: 34161391 DOI: 10.1371/journal.pone.0253445

Prodigiosin, a red linear tripyrrole pigment, has long been recognised for its antimicrobial property. However, the physiological contribution of prodigiosin to the survival of its producing hosts still remains undefined. Hence, the aim of this study was to investigate the biological role of prodigiosin from Serratia marcescens, particularly in microbial competition through its antimicrobial activity, towards the growth and secreted virulence factors of four clinical pathogenic bacteria (methicillin-resistant Staphylococcus aureus (MRSA), Enterococcus faecalis, Salmonella enterica serovar Typhimurium and Pseudomonas aeruginosa) as well as Staphylococcus aureus and Escherichia coli. Prodigiosin was first extracted from S. marcescens and its purity confirmed by absorption spectrum, high performance liquid chromatography (HPLC) and liquid chromatography-tandem mass spectrophotometry (LC-MS/MS). The extracted prodigiosin was antagonistic towards all the tested bacteria. A disc-diffusion assay showed that prodigiosin is more selective towards Gram-positive bacteria and inhibited the growth of MRSA, S. aureus and E. faecalis and Gram-negative E. coli. A minimum inhibitory concentration of 10 μg/μL of prodigiosin was required to inhibit the growth of S. aureus, E. coli and E. faecalis whereas > 10 μg/μL was required to inhibit MRSA growth. We further assessed the effect of prodigiosin towards bacterial virulence factors such as haemolysin and production of protease as well as on biofilm formation. Prodigiosin did not inhibit haemolysis activity of clinically associated bacteria but was able to reduce protease activity for MRSA, E. coli and E. faecalis as well as decrease E. faecalis, Salmonella Typhimurium and E. coli biofilm formation. Results of this study show that in addition to its role in inhibiting bacterial growth, prodigiosin also inhibits the bacterial virulence factor protease production and biofilm formation, two strategies employed by bacteria in response to microbial competition. As clinical pathogens were more resistant to prodigiosin, we propose that prodigiosin is physiologically important for S. marcescens to compete against other bacteria in its natural soil and surface water environments.

Matched MeSH terms: Biofilms/drug effects*; Biofilms/growth & development
Fulltext Bioactive Compounds from the Bornean Endemic Plant Goniothalamus longistipetes

Teo SP, Bhakta S, Stapleton P, Gibbons S

Antibiotics (Basel), 2020 Dec 16;9(12).
PMID: 33339285 DOI: 10.3390/antibiotics9120913

The present study aimed to screen plants for bioactive compounds with potential antibacterial activities. In our efforts to evaluate plants from Borneo, we isolated and elucidated the structures of four natural products from the bioactive fraction of a chloroform extract of Goniothalamus longistipetes using various chromatographic and spectroscopic techniques. The bioactive compounds were identified as a known styryllactone, (+)-altholactone ((2S,3R,3aS,7aS)-3-hydroxy-2-phenyl-2,3,3a,7a-tetrahydrobenzo-5(4H)-5-one) (1), a new styryllactone, (2S,3R,3aS,7aS)-3-hydroxy-2-phenyl-2,3,3a,7a-tetrahydrobenzo-5(4H)-5-one) (2) as well as a new alkaloid, 2,6-dimethoxyisonicotinaldehyde (3) and a new alkenyl-5-hydroxyl-phenyl benzoic acid (4). 1 and 4 showed broad-spectrum anti-bacterial activities against Gram-positive and Gram-negative bacteria as well as acid-fast model selected for this study. Compound 2 only demonstrated activities against Gram-positive bacteria whilst 3 displayed selective inhibitory activities against Gram-positive bacterial strains. Additionally, their mechanisms of anti-bacterial action were also investigated. Using Mycobacterium smegmatis as a fast-growing model of tubercle bacilli, compounds 1, 2 and 4 demonstrated inhibitory activities against whole-cell drug efflux and biofilm formation; two key intrinsic mechanisms of antibiotic resistance. Interestingly, the amphiphilic compound 4 exhibited inhibitory activity against the conjugation of plasmid pKM101 in Escherichia coli using a plate conjugation assay. Plasmid conjugation is a mechanism by which Gram-positive and Gram-negative-bacteria acquire drug resistance and virulence. These results indicated that bioactive compounds isolated from Goniothalamus longistipetes can be potential candidates as 'hits' for further optimisation.

Matched MeSH terms: Biofilms
Application of isolated halophilic microorganisms suspended and immobilized on walnut shell as biocarrier for treatment of oilfield produced water

Hasanzadeh R, Abbasi Souraki B, Pendashteh A, Khayati G, Ahmadun FR

J Hazard Mater, 2020 12 05;400:123197.
PMID: 32947738 DOI: 10.1016/j.jhazmat.2020.123197

Salinity expressed as total dissolved solids (TDS), is the most challenging parameter in bioremediation of produced water which may inhibit the microbial activities and cause sedimentation problems. The present study explores the feasibility of using walnut shell as an inexpensive and accessible adsorbent-carrier for the immobilization of isolated halophilic microorganisms for treatment of synthetic oilfield produced water. The moving bed biofilm reactor (MBBR) was examined with influent chemical oxygen demand (COD) concentrations from 900 to 3600 mg L-1, TDS concentrations from 35,000-200,000 mg L-1, and cycle times from 24 to 72 h. Comparison of the MBBR with the conventional sequencing batch reactor (SBR) indicated that both systems operated at lower influent COD and TDS concentrations satisfactorily; but at higher TDSs (above 150,000 mg L-1) the MBBR was more resistant to the shocks of toxicity (salinity) and organic load relative to the SBR. Also, the effluent turbidity was lower and the free sludge settling property was more favorable in the MBBR with average sludge volume index (SVI) of 38.8 mL g-1 compared to the SBR with SVI of 98.09 mL g-1. Microbial identification confirmed the presence of eight dominant halophilic species which were hydrocarbon degraders and/or denitrifiers.

Matched MeSH terms: Biofilms
Properties of a modified quaternary ammonium silane formulation as a potential root canal irrigant in endodontics

Daood U, Parolia A, Matinlinna J, Yiu C, Ahmed HMA, Fawzy A

Dent Mater, 2020 12;36(12):e386-e402.
PMID: 33010944 DOI: 10.1016/j.dental.2020.09.008

OBJECTIVES: Evaluate a new modified quaternary ammonium silane irrigant solution for its antimicrobial, cytotoxic and mechanical properties of dentine substrate.
METHODS: Root canal preparation was performed using stainless steel K-files™ and F4 size protaper with irrigation protocols of 6% NaOCl + 2% CHX; 3.5% QIS; 2% QIS and sterile saline. Biofilms were prepared using E. faecalis adjusted and allowed to grow for 3 days, treated with irrigants, and allowed to grow for 7 days. AFM was performed and surface free energy calculated. MC3T3 cells were infected with endo irrigant treated E. faecalis biofilms. Raman spectroscopy of biofilms were performed after bacterial re-growth on root dentine and exposed to different irrigation protocols and collagen fibers analysed collagen fibers using TEM. Antimicrobial potency against E. faecalis biofilms and cytoxicity against 3T3 NIH cells were also. Resin penetration and MitoTracker green were also evaluated for sealer penetration and mitochondrial viability. Data were analysed using One-way ANOVA, principal component analysis and post-hoc Fisher's least-significant difference.
RESULTS: Elastic moduli were maintained amongst control (5.5 ± 0.9) and 3.5% QIS (4.4 ± 1.1) specimens with surface free energy higher in QIS specimens. MC3T3 cells showed reduced viability in 6%NaOCl+2%CHX specimens compared to QIS specimens. DNA/purine were expressed in increased intensities in control and 6% NaOCl + 2% CHX specimens with bands around 480-490 cm-1 reduced in QIS specimens. 3.5% QIS specimens showed intact collagen fibrillar network and predominantly dead bacterial cells in confocal microscopy. 3.5% QIS irrigant formed a thin crust-type surface layer with cytoplasmic extensions of 3T3NIH spread over root dentine. Experiments confirmed MitoTracker accumulation in 3.5% treated cells.
SIGNIFICANCE: Novel QIS root canal irrigant achieved optimum antimicrobial protection inside the root canals facilitating a toxic effect against the Enterococcus faecalis biofilm. Root dentine substrates exhibited optimum mechanical properties and there was viability of fibroblastic mitochondria.

Matched MeSH terms: Biofilms
Fulltext Prevalence, virulence and antifungal activity of C. albicans isolated from infected root canals

Abraham SB, Al Marzooq F, Himratul-Aznita WH, Ahmed HMA, Samaranayake LP

BMC Oral Health, 2020 12 01;20(1):347.
PMID: 33256696 DOI: 10.1186/s12903-020-01347-5

BACKGROUND: There is limited data on the prevalence of Candida species in infected root canal systems of human teeth. We attempted to investigate the prevalence, genotype, virulence and the antifungal susceptibility of Candida albicans isolated from infected root canals of patients with primary and post-treatment infections in a UAE population.
METHODS: Microbiological samples from 71 subjects with infected root canals were aseptically collected, and cultured on Sabouraud dextrose agar, and C. albicans was identified using multiplex polymerase chain reaction, and the isolates were further subtyped using ABC genotyping system. Their relative virulence was compared using further four archival samples of endodontic origin from another geographical region, and four more salivary isolates, as controls. The virulence attributes compared were biofilm formation, and production of phospholipase and haemolysin, and the susceptibility to nystatin, amphotericin B, ketoconazole, and fluoconazole was also tested.
RESULTS: 4 out of 71 samples (5.6%) yielded Candida species. On analysis of variance among the groups, the intracanal isolates, mainly Genotype A, possessed a high degree of phospholipase and haemolysin activity (p

Matched MeSH terms: Biofilms
Fulltext First reported case of Gilbertella persicaria in human stool: outcome of a community study from Segamat, Johor, Malaysia

Huët MAL, Wong LW, Goh CBS, Ong KS, Dwiyanto J, Reidpath D, et al.

Braz J Microbiol, 2020 Dec;51(4):2067-2075.
PMID: 32572838 DOI: 10.1007/s42770-020-00323-z

Species of fungi belonging to the order Mucorales can be found everywhere in the environment. Gilbertella persicaria, which belongs to this order, have often been isolated from fruits and in water systems. However, there has been no report of isolation of this fungus from human samples. During a gut mycobiome study, from the Segamat community, Gilbertella persicaria was isolated from a human fecal sample and was characterized through a series of morphological assessment, biochemical tests, and molecular techniques. The isolate produced a white velvety surface that turned grayish after 24 h. Although no biofilm production was observed, the results indicated that the isolate could form calcium oxalate crystals, produced urease, and was resistant to low pH. The isolate was sensitive to amphotericin but resistant to voriconazole and itraconazole. The features of this fungus that could help in its survival in the human gut are also discussed.

Matched MeSH terms: Biofilms/growth & development

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