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Fulltext Antibiotic Resistant and Virulence Determinants of Staphylococcus haemolyticus C10A as Revealed by Whole Genome Sequencing

Chan KG, Ng KT, Chong TM, Pang YK, Kamarulzaman A, Yin WF, et al.

J Genomics, 2015;3:72-4.
PMID: 26157506 DOI: 10.7150/jgen.12574

Staphylococcus haemolyticus is one of the pathogens that harbor a high level of antibiotic resistance. Here, we highlighted the potential determinants for multidrug resistance and virulence from the draft genome of Staphylococcus haemolyticus strain C10A, isolated from a patient with chronic obstructive pulmonary disease exacerbation.
Fulltext Anticancer Activities of Surfactin and Potential Application of Nanotechnology Assisted Surfactin Delivery

Wu YS, Ngai SC, Goh BH, Chan KG, Lee LH, Chuah LH

Front Pharmacol, 2017;8:761.
PMID: 29123482 DOI: 10.3389/fphar.2017.00761

Surfactin, a cyclic lipopeptide biosurfactant produced by various strains of Bacillus genus, has been shown to induce cytotoxicity against many cancer types, such as Ehrlich ascites, breast and colon cancers, leukemia and hepatoma. Surfactin treatment can inhibit cancer progression by growth inhibition, cell cycle arrest, apoptosis, and metastasis arrest. Owing to the potent effect of surfactin on cancer cells, numerous studies have recently investigated the mechanisms that underlie its anticancer activity. The amphiphilic nature of surfactin allows its easy incorporation nano-formulations, such as polymeric nanoparticles, micelles, microemulsions, liposomes, to name a few. The use of nano-formulations offers the advantage of optimizing surfactin delivery for an improved anticancer therapy. This review focuses on the current knowledge of surfactin properties and biosynthesis; anticancer activity against different cancer models and the underlying mechanisms involved; as well as the potential application of nano-formulations for optimal surfactin delivery.
Fulltext Anticancer Drug Discovery from Microbial Sources: The Unique Mangrove Streptomycetes

Law JW, Law LN, Letchumanan V, Tan LT, Wong SH, Chan KG, et al.

Molecules, 2020 Nov 17;25(22).
PMID: 33212836 DOI: 10.3390/molecules25225365

Worldwide cancer incidence and mortality have always been a concern to the community. The cancer mortality rate has generally declined over the years; however, there is still an increased mortality rate in poorer countries that receives considerable attention from healthcare professionals. This suggested the importance of the prompt detection, effective treatment, and prevention strategies. The genus Streptomyces has been documented as a prolific producer of biologically active secondary metabolites. Streptomycetes from mangrove environments attract researchers' attention due to their ability to synthesize diverse, interesting bioactive metabolites. The present review highlights research on mangrove-derived streptomycetes and the production of anticancer-related compounds from these microorganisms. Research studies conducted between 2008 and 2019, specifically mentioning the isolation of streptomycetes from mangrove areas and described the successful purification of compound(s) or generation of crude extracts with cytotoxic activity against human cancer cell lines, were compiled in this review. It is anticipated that there will be an increase in prospects for mangrove-derived streptomycetes as one of the natural resources for the isolation of chemotherapeutic agents.
Fulltext Antioxidant Activities of Streptomyces sp. strain MUSC 14 from Mangrove Forest Soil in Malaysia

Kemung HM, Tan LT, Chan KG, Ser HL, Law JW, Lee LH, et al.

Biomed Res Int, 2020;2020:6402607.
PMID: 32258133 DOI: 10.1155/2020/6402607

The mangrove ecosystem of Malaysia remains yet to be fully explored for potential microbes that produce biologically active metabolites. In the present study, a mangrove-derived Streptomyces sp. strain MUSC 14 previously isolated from the state of Pahang, Malaysia Peninsula, was studied for its potential in producing antioxidant metabolites. The identity of Streptomyces sp. strain MUSC14 was consistent with the genotypic and phenotypic characteristics of the Streptomyces genus. The antioxidant potential of Streptomyces sp. strain MUSC 14 was determined through screening of its methanolic extract against sets of antioxidant assays. The results were indicative of Streptomyces sp. strain MUSC 14 displaying strong antioxidant activity against ABTS, DPPH free radicals and metal chelating activity of 62.71 ± 3.30%, 24.71 ± 2.22%, and 55.82 ± 2.35%, respectively. The result of ferric reducing activity measured in terms of dose was equivalent to 2.35-2.45 μg of positive control ascorbic acid. Furthermore, there was a high correlation between the total phenolic content and the antioxidant activities with r = 0.979, r = 0.858, and r = 0.983 representing ABTS, DPPH, and metal chelation, respectively. Overall, the present study suggests that Streptomyces sp. strain MUSC 14 from mangrove forest soil has potential to produce antioxidant metabolites that can be further exploited for therapeutic application.
Fulltext Antioxidative Potential of a Streptomyces sp. MUM292 Isolated from Mangrove Soil

Tan LT, Chan KG, Chan CK, Khan TM, Lee LH, Goh BH

Biomed Res Int, 2018;2018:4823126.
PMID: 29805975 DOI: 10.1155/2018/4823126

Mangrove derived microorganisms constitute a rich bioresource for bioprospecting of bioactive natural products. This study explored the antioxidant potentials of Streptomyces bacteria derived from mangrove soil. Based on 16S rRNA phylogenetic analysis, strain MUM292 was identified as the genus Streptomyces. Strain MUM292 showed the highest 16S rRNA gene sequence similarity of 99.54% with S. griseoruber NBRC12873T. Furthermore, strain MUM292 was also characterized and showed phenotypic characteristics consistent with Streptomyces bacteria. Fermentation and extraction were performed to obtain the MUM292 extract containing the secondary metabolites of strain MUM292. The extract displayed promising antioxidant activities, including DPPH, ABTS, and superoxide radical scavenging and also metal-chelating activities. The process of lipid peroxidation in lipid-rich product was also retarded by MUM292 extract and resulted in reduced MDA production. The potential bioactive constituents of MUM292 extract were investigated using GC-MS and preliminary detection showed the presence of pyrazine, pyrrole, cyclic dipeptides, and phenolic compound in MUM292 extract. This work demonstrates that Streptomyces MUM292 can be a potential antioxidant resource for food and pharmaceutical industries.
Fulltext Aquella oligotrophica gen. nov. sp. nov.: A new member of the family Neisseriaceae isolated from laboratory tap water

Chan KG, See-Too WS, Chua KO, Peix Á, Goh KM, Hong KW, et al.

Microbiologyopen, 2019 Jul;8(7):e00793.
PMID: 30656855 DOI: 10.1002/mbo3.793

A bacterial strain designated as P08T was isolated from laboratory tap water during a water quality assessment in University of Malaya, Malaysia. The strain was a Gram-negative, rod-shaped, nonmotile, and aerobic bacterium. Complete genome of P08T comprised of a 2,820,660 bp chromosome with a G + C content of 36.43%. Both 16S rRNA phylogeny and phylogenetic tree inferred from the core gene matrix demonstrated that P08T formed a hitherto unknown subline within the family Neisseriaceae. Ortho average nucleotide identity (OrthoANI) values and the percentage of conserved proteins (POCP) calculated from complete genome sequence indicated low relatedness between P08T and its phylogenetic neighbors. Respiratory quinone analysis revealed Q-8 as the only detectable quinone. The predominant cellular fatty acids were identified as C14:0 , iso-C15:0 , and summed feature 3 (C16:1 ω7c/C16:1 ω6c). The polar lipids consisted of uncharacterized aminolipid, phosphatidylglycerol, and phosphatidylethanolamine. All aspects of phenotypic and phylogenetic data suggested that strain P08T represents a novel genus within family Neisseriaceae, for which the name Aquella gen. nov. is proposed. The type species of the genus is Aquella oligotrophica sp. nov., and the type strain is P08T (=LMG 29629T =DSM 100970T ).
Fulltext Association of diabetes knowledge with glycemic control and self-care practices among Pakistani people with type 2 diabetes mellitus

Bukhsh A, Khan TM, Sarfraz Nawaz M, Sajjad Ahmed H, Chan KG, Goh BH

Diabetes Metab Syndr Obes, 2019;12:1409-1417.
PMID: 31616171 DOI: 10.2147/DMSO.S209711

Objective: This study explored the relationship of disease knowledge with glycemic control and self-care practices in adult Pakistani people diabetes (PWD).
Methods: People diagnosed with type 2 diabetes (n=218) were selected from three health care centers, located in different cities of Pakistan. Disease knowledge and self-care practices were assessed by Urdu versions of Diabetes Knowledge Questionnaire (DKQ) and Diabetes Self-Management Questionnaire (DSMQ), using a cross-sectional design. Chi-square and correlation analysis were applied to explore the relationship of disease knowledge with glycemic control and self-care practices. Linear regression was used to explore the predictors for disease knowledge.
Results: Majority of the sample was >45-60 years old (48.8%), suffering from type 2 diabetes mellitus for <5 years (49.5%) and had poor glycemic control (HbA1C≥7%; n=181 participants). Disease knowledge was significantly associated (p<0.05) with patient's gender, level of education, family history of diabetes, nature of euglycemic therapy, and glycemic control. Correlation matrix showed strongly inverse correlations of DKQ with glycated hemoglobin levels (r=-0.62; p<0.001) and strongly positive with DSMQ sum scale (r=0.63; p<0.001). PWD having university-level education (β=0.22; 95% Confidence Interval (CI) 0.189, 0.872; p<0.01), doing job (β=0.22; 95% CI 0.009, 0.908]; p=0.046), and use of oral hypoglycemic agents in combination with insulin (β=-0.16; 95% CI [-1.224, -0.071]; p=0.028) were the significant predictors for disease knowledge.
Conclusion: Disease knowledge significantly correlated with glycated hemoglobin levels and self-care activities of PWD. These findings will help in designing patient-tailored diabetes educational interventions for yielding a higher probability of achieving target glycemic control.
Fulltext Association of diabetes-related self-care activities with glycemic control of patients with type 2 diabetes in Pakistan

Bukhsh A, Khan TM, Nawaz MS, Ahmed HS, Chan KG, Lee LH, et al.

Patient Prefer Adherence, 2018;12:2377-2385.
PMID: 30519003 DOI: 10.2147/PPA.S177314

Objective: Association of various self-care activities on glycemic control of people with diabetes (PWD) in Pakistan is yet to be explored. The current study aimed to evaluate the association of various diabetes-related self-care activities with glycated hemoglobin (HbA1c) levels and to examine the predictive relationship of patients' demographic variables with their self-care activities.

Patients and methods: A cross-sectional study was conducted on adult PWD (N=218) who were diagnosed with type 2 diabetes mellitus of at least 1 year duration. Self-care activities were examined by using the Urdu version of Diabetes Self-management Questionnaire. Linear regression analysis was conducted to examine the significant predictors for diabetes-related self-care activities and glycemic control.

Results: Mean age of the patients was 50.77±13.3 years. Poor glycemic control (HbA1c $7%) was observed in majority of the patients (83%). Linear regression analysis revealed that glucose management (β=-0.44; 95% CI -0.438, -0.209; P<0.001) was the strongest predictor for low levels of patients' HbA1c, followed by dietary control (β=-0.19; 95% CI -0.248, -0.018; P=0.024) and physical activity (β=-0.17; 95% CI -0.165, -0.023; P=0.010), respectively. Linear regression analysis showed that use of oral hypoglycemic agents only (β=-0.218; 95% CI -0.956, -0.200; P=0.003) and higher education level (β=0.204; 95% CI 0.138, 0.777; P=0.005) were significant predictors for higher scores of patients' self-care activities.

Conclusion: The findings support that PWD having better self-reported self-care activities achieve better glycemic control. Patients' self-care activities should be monitored on a regular basis, especially for those who are at risk of poor glycemic control.
Fulltext Author Correction: Streptomyces monashensis sp. nov., a novel mangrove soil actinobacterium from East Malaysia with antioxidative potential

Law JW, Ser HL, Ab Mutalib NS, Saokaew S, Duangjai A, Khan TM, et al.

Sci Rep, 2020 Jan 10;10(1):319.
PMID: 31924829 DOI: 10.1038/s41598-019-55964-4

An amendment to this paper has been published and can be accessed via a link at the top of the paper.
Fulltext Beneficial Role of Carica papaya Extracts and Phytochemicals on Oxidative Stress and Related Diseases: A Mini Review

Kong YR, Jong YX, Balakrishnan M, Bok ZK, Weng JKK, Tay KC, et al.

Biology (Basel), 2021 Apr 01;10(4).
PMID: 33916114 DOI: 10.3390/biology10040287

Oxidative stress is a result of disruption in the balance between antioxidants and pro-oxidants in which subsequently impacting on redox signaling, causing cell and tissue damages. It leads to a range of medical conditions including inflammation, skin aging, impaired wound healing, chronic diseases and cancers but these conditions can be managed properly with the aid of antioxidants. This review features various studies to provide an overview on how Carica papaya help counteract oxidative stress via various mechanisms of action closely related to its antioxidant properties and eventually improving the management of various oxidative stress-related health conditions. Carica papaya is a topical plant species discovered to contain high amounts of natural antioxidants that can usually be found in their leaves, fruits and seeds. It contains various chemical compounds demonstrate significant antioxidant properties including caffeic acid, myricetin, rutin, quercetin, α-tocopherol, papain, benzyl isothiocyanate (BiTC), and kaempferol. Therefore, it can counteract pro-oxidants via a number of signaling pathways that either promote the expression of antioxidant enzymes or reduce ROS production. These signaling pathways activate the antioxidant defense mechanisms that protect the body against both intrinsic and extrinsic oxidative stress. To conclude, Carica papaya can be incorporated into medications or supplements to help manage the health conditions driven by oxidative stress and further studies are needed to investigate the potential of its chemical components to manage various chronic diseases.
Fulltext Bile Sensing: The Activation of Vibrio parahaemolyticus Virulence

Letchumanan V, Chan KG, Khan TM, Bukhari SI, Ab Mutalib NS, Goh BH, et al.

Front Microbiol, 2017;8:728.
PMID: 28484445 DOI: 10.3389/fmicb.2017.00728

Bacteria must develop resistance to various inhospitable conditions in order to survive in the human gastrointestinal tract. Bile, which is secreted by the liver, and plays an important role in food digestion also has antimicrobial properties and is able to disrupt cellular homeostasis. Paradoxically, although bile is one of the guts defenses, many studies have reported that bacteria such as Vibrio parahaemolyticus can sense bile and use its presence as an environmental cue to upregulate virulence genes during infection. This article aims to discuss how bile is detected by V. parahaemolyticus and its role in regulating type III secretion system 2 leading to human infection. This bile-bacteria interaction pathway gives us a clearer understanding of the biochemical and structural analysis of the bacterial receptors involved in mediating a response to bile salts which appear to be a significant environmental cue during initiation of an infection.
Biotic inactivation of the Pseudomonas aeruginosa quinolone signal molecule

Soh EY, Chhabra SR, Halliday N, Heeb S, Müller C, Birmes FS, et al.

Environ Microbiol, 2015 Nov;17(11):4352-65.
PMID: 25809238 DOI: 10.1111/1462-2920.12857

In Pseudomonas aeruginosa, quorum sensing (QS) regulates the production of secondary metabolites, many of which are antimicrobials that impact on polymicrobial community composition. Consequently, quenching QS modulates the environmental impact of P. aeruginosa. To identify bacteria capable of inactivating the QS signal molecule 2-heptyl-3-hydroxy-4(1H)-quinolone (PQS), a minimal medium containing PQS as the sole carbon source was used to enrich a Malaysian rainforest soil sample. This yielded an Achromobacter xylosoxidans strain (Q19) that inactivated PQS, yielding a new fluorescent compound (I-PQS) confirmed as PQS-derived using deuterated PQS. The I-PQS structure was elucidated using mass spectrometry and nuclear magnetic resonance spectroscopy as 2-heptyl-2-hydroxy-1,2-dihydroquinoline-3,4-dione (HHQD). Achromobacter xylosoxidans Q19 oxidized PQS congeners with alkyl chains ranging from C1 to C5 and also N-methyl PQS, yielding the corresponding 2-hydroxy-1,2-dihydroquinoline-3,4-diones, but was unable to inactivate the PQS precursor HHQ. This indicates that the hydroxyl group at position 3 in PQS is essential and that A. xylosoxidans inactivates PQS via a pathway involving the incorporation of oxygen at C2 of the heterocyclic ring. The conversion of PQS to HHQD also occurred on incubation with 12/17 A. xylosoxidans strains recovered from cystic fibrosis patients, with P. aeruginosa and with Arthrobacter, suggesting that formation of hydroxylated PQS may be a common mechanism of inactivation.
Fulltext COVID-19: Insights into Potential Vaccines

Loo KY, Letchumanan V, Ser HL, Teoh SL, Law JW, Tan LT, et al.

Microorganisms, 2021 Mar 15;9(3).
PMID: 33804162 DOI: 10.3390/microorganisms9030605

People around the world ushered in the new year 2021 with a fear of COVID-19, as family members have lost their loved ones to the disease. Millions of people have been infected, and the livelihood of many has been jeopardized due to the pandemic. Pharmaceutical companies are racing against time to develop an effective vaccine to protect against COVID-19. Researchers have developed various types of candidate vaccines with the release of the genetic sequence of the SARS-CoV-2 virus in January. These include inactivated viral vaccines, protein subunit vaccines, mRNA vaccines, and recombinant viral vector vaccines. To date, several vaccines have been authorized for emergency use and they have been administered in countries across the globe. Meanwhile, there are also vaccine candidates in Phase III clinical trials awaiting results and approval from authorities. These candidates have shown positive results in the previous stages of the trials, whereby they could induce an immune response with minimal side effects in the participants. This review aims to discuss the different vaccine platforms and the clinical trials of the candidate vaccines.
Fulltext Caffeine as a potential quorum sensing inhibitor

Norizan SN, Yin WF, Chan KG

Sensors (Basel), 2013;13(4):5117-29.
PMID: 23598500 DOI: 10.3390/s130405117

Quorum sensing enables bacteria to control the gene expression in response to the cell density. It regulates a variety of bacterial physiological functions such as biofilm formation, bioluminescence, virulence factors and swarming which has been shown contribute to bacterial pathogenesis. The use of quorum sensing inhibitor would be of particular interest in treating bacterial pathogenicity and infections. In this work, we have tested caffeine as quorum sensing inhibitor by using Chromobacterium violaceum CV026 as a biosensor. We verified that caffeine did not degrade the N-acyl homoserine lactones tested. In this work, it is shown that caffeine could inhibit N-acyl homoserine lactone production and swarming of a human opportunistic pathogen, namely Pseudomonas aeruginosa PA01. To the best of our knowledge, this is the first documentation providing evidence on the presence of anti-quorum sensing activity in caffeine. Our work will allow caffeine to be explored as anti-infective drugs.
Care demands on mothers caring for a child with Down syndrome: Malaysian (Sarawak) mothers' perspectives

Chan KG, Lim KA, Ling HK

Int J Nurs Pract, 2015 Oct;21(5):522-31.
PMID: 24674378 DOI: 10.1111/ijn.12275

This paper examines the experiences of mothers caring for a child with Down syndrome in the Malaysian (Sarawak) context. Qualitative interviews were conducted with 26 biological mothers of children with Down syndrome aged 18 years and below. They were accessed through selected child health clinics, community-based rehabilitation centres and schools using purposive sampling within two regions in Sarawak, one of the two Borneo States of Malaysia. Major themes emerging within the context of care demands were children's health, developmental delays, daily needs and behaviour issues. The insights obtained into the care demands experienced by mothers of children with Down syndrome have several implications for practice by care professionals.
Fulltext Characterisation of a marine bacterium Vibrio brasiliensis T33 producing N-acyl homoserine lactone quorum sensing molecules

Tan WS, Yunos NY, Tan PW, Mohamad NI, Adrian TG, Yin WF, et al.

Sensors (Basel), 2014;14(7):12104-13.
PMID: 25006994 DOI: 10.3390/s140712104

N-acylhomoserine lactones (AHL) plays roles as signal molecules in quorum sensing (QS) in most Gram-negative bacteria. QS regulates various physiological activities in relation with population density and concentration of signal molecules. With the aim of isolating marine water-borne bacteria that possess QS properties, we report here the preliminary screening of marine bacteria for AHL production using Chromobacterium violaceum CV026 as the AHL biosensor. Strain T33 was isolated based on preliminary AHL screening and further identified by using 16S rDNA sequence analysis as a member of the genus Vibrio closely related to Vibrio brasiliensis. The isolated Vibrio sp. strain T33 was confirmed to produce N-hexanoyl-L-homoserine lactone (C6-HSL) and N-(3-oxodecanoyl)-L-homoserine lactone (3-oxo-C10 HSL) through high resolution tandem mass spectrometry analysis. We demonstrated that this isolate formed biofilms which could be inhibited by catechin. To the best of our knowledge, this is the first report that documents the production of these AHLs by Vibrio brasiliensis strain T33.
Characterization and Comparative Overview of Complete Sequences of the First Plasmids of Pandoraea across Clinical and Non-clinical Strains

Yong D, Tee KK, Yin WF, Chan KG

Front Microbiol, 2016;7:1606.
PMID: 27790203

To date, information on plasmid analysis in Pandoraea spp. is scarce. To address the gap of knowledge on this, the complete sequences of eight plasmids from Pandoraea spp. namely Pandoraea faecigallinarum DSM 23572(T) (pPF72-1, pPF72-2), Pandoraea oxalativorans DSM 23570(T) (pPO70-1, pPO70-2, pPO70-3, pPO70-4), Pandoraea vervacti NS15 (pPV15) and Pandoraea apista DSM 16535(T) (pPA35) were studied for the first time in this study. The information on plasmid sequences in Pandoraea spp. is useful as the sequences did not match any known plasmid sequence deposited in public databases. Replication genes were not identified in some plasmids, a situation that has led to the possibility of host interaction involvement. Some plasmids were also void of par genes and intriguingly, repA gene was also not discovered in these plasmids. This further leads to the hypothesis of host-plasmid interaction. Plasmid stabilization/stability protein-encoding genes were observed in some plasmids but were not established for participating in plasmid segregation. Toxin-antitoxin systems MazEF, VapBC, RelBE, YgiT-MqsR, HigBA, and ParDE were identified across the plasmids and their presence would improve plasmid maintenance. Conjugation genes were identified portraying the conjugation ability amongst Pandoraea plasmids. Additionally, we found a shared region amongst some of the plasmids that consists of conjugation genes. The identification of genes involved in replication, segregation, toxin-antitoxin systems and conjugation, would aid the design of drugs to prevent the survival or transmission of plasmids carrying pathogenic properties. Additionally, genes conferring virulence and antibiotic resistance were identified amongst the plasmids. The observed features in the plasmids shed light on the Pandoraea spp. as opportunistic pathogens.
Fulltext Characterization and Transcriptome Studies of Autoinducer Synthase Gene from Multidrug Resistant Acinetobacter baumannii Strain 863

Ng CK, How KY, Tee KK, Chan KG

Genes (Basel), 2019 04 08;10(4).
PMID: 30965610 DOI: 10.3390/genes10040282

Quorum sensing (QS) is a cell-to-cell communication system that uses autoinducers as signaling molecules to enable inter-species and intra-species interactions in response to external stimuli according to the population density. QS allows bacteria such as Acinetobacter baumannii to react rapidly in response to environmental changes and hence, increase the chances of survival. A. baumannii is one of the causative agents in hospital-acquired infections and the number of cases has increased remarkably in the past decade. In this study, A. baumannii strain 863, a multidrug-resistant pathogen, was found to exhibit QS activity by producing N-acyl homoserine lactone. We identified the autoinducer synthase gene, which we named abaI, by performing whole genome sequencing analysis of A. baumannii strain 863. Using high resolution tandem triple quadrupole mass spectrometry, we reported that abaI of A. baumannii strain 863 produced 3-hydroxy-dodecanoyl-homoserine lactone. A gene deletion mutant was constructed, which confirmed the functionality of abaI. A growth defect was observed in the QS-deficient mutant strain. Transcriptome profiling was performed to determine the possible genes regulated by QS. Four groups of genes that showed differential expression were discovered, namely those involved in carbon source metabolism, energy production, stress response and the translation process.
Fulltext Characterization of N-acylhomoserine lactone-degrading bacteria associated with the Zingiber officinale (ginger) rhizosphere: co-existence of quorum quenching and quorum sensing in Acinetobacter and Burkholderia

Chan KG, Atkinson S, Mathee K, Sam CK, Chhabra SR, Cámara M, et al.

BMC Microbiol, 2011 Mar 08;11:51.
PMID: 21385437 DOI: 10.1186/1471-2180-11-51

BACKGROUND: Cell-to-cell communication (quorum sensing (QS)) co-ordinates bacterial behaviour at a population level. Consequently the behaviour of a natural multi-species community is likely to depend at least in part on co-existing QS and quorum quenching (QQ) activities. Here we sought to discover novel N-acylhomoserine lactone (AHL)-dependent QS and QQ strains by investigating a bacterial community associated with the rhizosphere of ginger (Zingiber officinale) growing in the Malaysian rainforest.
RESULTS: By using a basal growth medium containing N-(3-oxohexanoyl)homoserine lactone (3-oxo-C6-HSL) as the sole source of carbon and nitrogen, the ginger rhizosphere associated bacteria were enriched for strains with AHL-degrading capabilities. Three isolates belonging to the genera Acinetobacter (GG2), Burkholderia (GG4) and Klebsiella (Se14) were identified and selected for further study. Strains GG2 and Se14 exhibited the broadest spectrum of AHL-degrading activities via lactonolysis while GG4 reduced 3-oxo-AHLs to the corresponding 3-hydroxy compounds. In GG2 and GG4, QQ was found to co-exist with AHL-dependent QS and GG2 was shown to inactivate both self-generated and exogenously supplied AHLs. GG2, GG4 and Se14 were each able to attenuate virulence factor production in both human and plant pathogens.
CONCLUSIONS: Collectively our data show that ginger rhizosphere bacteria which make and degrade a wide range of AHLs are likely to play a collective role in determining the QS-dependent phenotype of a polymicrobial community.
Fulltext Characterization of a glucose-tolerant β-glucosidase from Anoxybacillus sp. DT3-1

Chan CS, Sin LL, Chan KG, Shamsir MS, Manan FA, Sani RK, et al.

Biotechnol Biofuels, 2016;9(1):174.
PMID: 27555880 DOI: 10.1186/s13068-016-0587-x

In general, biofuel production involves biomass pretreatment and enzymatic saccharification, followed by the subsequent sugar conversion to biofuel via fermentation. The crucial step in the production of biofuel from biomass is the enzymatic saccharification. Many of the commercial cellulase enzyme cocktails, such as Spezyme(®) CP (Genencor), Acellerase™ 1000 (Genencor), and Celluclast(®) 1.5L (Novozymes), are ineffectively to release free glucose from the pretreated biomass without additional β-glucosidase.

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