Serratia marcescens is an opportunistic bacterial pathogen with broad range of host ranging from vertebrates, invertebrates and plants. S. marcescens strain W2.3 was isolated from a diseased tilapia fish and it was suspected to be the causal agent for the fish disease as virulence genes were found within its genome. In this study, for the first time, the genome sequences of S. marcescens strain W2.3 were sequenced using the Illumina MiSeq platform.
Quorum sensing is a unique bacterial communication system which permits bacteria to synchronize their behaviour in accordance with the population density. The operation of this communication network involves the use of diffusible autoinducer molecules, termed N-acylhomoserine lactones (AHLs). Serratia spp. are well known for their use of quorum sensing to regulate the expression of various genes. In this study, we aimed to characterized the AHL production of a bacterium designated as strain RB-25 isolated from a former domestic waste landfill site. It was identified as Serratia fonticola using matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry analysis and this was confirmed by 16S ribosomal DNA sequencing. High resolution triple quadrupole liquid chromatography-mass spectrometry analysis of S. fonticola strain RB-25 spent culture supernatant indicated the existence of three AHLs namely: N-butyryl-L-homoserine lactone (C4-HSL), N-hexanoyl-L-homoserine lactone (C6-HSL) and N-(3-oxohexanoyl) homoserine-lactone (3-oxo-C6 HSL). This is the first report of the production of these AHLs in S. fonticola.
A novel bacterium, strain MUSC 273(T), was isolated from mangrove sediments of the Tanjung Lumpur river in the state of Pahang in peninsular Malaysia. The bacterium was yellow-pigmented, Gram-negative, rod-shaped and non-spore-forming. The taxonomy of strain MUSC 273(T) was studied by a polyphasic approach and the organism showed a range of phenotypic and chemotaxonomic properties consistent with those of the genus Novosphingobium. The 16S rRNA gene sequence of strain MUSC 273(T) showed the highest sequence similarity to those of Novosphingobium indicum H25(T) (96.8 %), N. naphthalenivorans TUT562(T) (96.4 %) and N. soli CC-TPE-1(T) (95.9 %) and lower sequence similarity to members of all other species of the genus Novosphingobium. Furthermore, in phylogenetic analyses based on the 16S rRNA gene sequence, strain MUSC 273(T) formed a distinct cluster with members of the genus Novosphingobium. DNA-DNA relatedness of strain MUSC 273(T) to the type strains of the most closely related species, N. indicum MCCC 1A01080(T) and N. naphthalenivorans DSM 18518(T), was 29.2 % (reciprocal 31.0 %) and 17 % (reciprocal 18 %), respectively. The major respiratory quinone was ubiquinone Q-10, the major polyamine was spermidine and the DNA G+C content was 63.3±0.1 mol%. The polar lipids consisted of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylmethylethanolamine, phosphatidyldimethylethanolamine, phosphatidylcholine and sphingoglycolipid. The major fatty acids were C18 : 1ω7c, C17 : 1ω6c, C16 : 0, C15 : 0 2-OH and C16 : 1ω7c. Comparison of BOX-PCR fingerprints indicated that strain MUSC 273(T) represented a unique DNA profile. The combined genotypic and phenotypic data showed that strain MUSC 273(T) represents a novel species of the genus Novosphingobium, for which the name Novosphingobium malaysiense sp. nov. is proposed. The type strain is MUSC 273(T) ( = DSM 27798(T) = MCCC 1A00645(T) = NBRC 109947(T)).
Quorum sensing (QS) is a mechanism adopted by bacteria to regulate expression of genes according to population density. N-acylhomoserine lactones (AHLs) are a type of QS signalling molecules commonly found in Gram-negative bacteria which have been reported to play a role in microbial spoilage of foods and pathogenesis. In this study, we isolated an AHL-producing Hafnia alvei strain (FB1) from spherical fish pastes. Analysis via high resolution triple quadrupole liquid chromatography/mass spectrometry (LC/MS) on extracts from the spent supernatant of H. alvei FB1 revealed the existence of two short chain AHLs: N-(3-oxohexanoyl) homoserine lactone (3-oxo-C6-HSL) and N-(3-oxo- octanoyl) homoserine lactone (3-oxo-C8-HSL). To our knowledge, this is the first report of the production of AHLs, especially 3-oxo-C8-HSL, by H. alvei.
Quorum sensing is a well-studied cell-to-cell communication method that involves a cell-density dependent regulation of genes expression mediated by signalling molecules. In this study, a bacterium isolated from a plant material compost pile was found to possess quorum sensing activity based on bioassay screening. Isolate YL12 was identified using matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry and molecular typing using rpoD gene which identified the isolate as Aeromonas caviae. High resolution tandem mass spectrometry was subsequently employed to identify the N-acyl homoserine lactone profile of Aeromonas caviae YL12 and confirmed that this isolate produced two short chain N-acyl homoserine lactones, namely C4-HSL and C6, and the production was observed to be cell density-dependent. Using the thin layer chromatography (TLC) bioassay, both AHLs were found to activate C. violaceum CV026, whereas only C6-HSL was revealed to induce bioluminescence expression of E. coli [pSB401]. The data presented in this study will be the leading steps in understanding the role of quorum sensing in Aeromonas caviae strain YL12.
The aim of this study was to investigate the mode of action of the lavender essential oil (LV) on antimicrobial activity against multi-drug-resistant Escherichia coli J53 R1 when used singly and in combination with piperacillin.
A novel actinobacterial strain, designated MUSC 201T, was isolated from a mangrove soil collected from Kuantan, the capital city of Pahang State in Malaysia. The taxonomic status of this strain was determined using a polyphasic approach. Comparative 16S rRNA gene sequence analysis revealed that strain MUSC 201T represented a novel lineage within the class Actinobacteria. Strain MUSC 201T formed a distinct clade in the family Nocardioidaceae and was most closely related to the members of the genera Nocardioides (16S rRNA gene sequence similarity, 91.9-95.1%), Aeromicrobium (92.7-94.6%), Marmoricola (92.5-93.1%) and Kribbella (91.5-92.4%). The cells of this strain were irregular coccoid to short rod shaped. The peptidoglycan contained ll-diaminopimelic acid as diagnostic diamino acid and the peptidoglycan type was A3γ. The peptidoglycan cell wall contained ll-diaminopimelic acid, glycine, glutamic acid and alanine in a molar ratio of 1.5:0.9:1.0:1.5. The cell-wall sugars were galactose and rhamnose. The predominant menaquinone was MK-9(H4). The polar lipids consisted of diphosphatidylglycerol, phosphatidylglycerol, phosphoglycolipid, glycolipid and four unknown phospholipids. The major cellular fatty acids were C18:1ω9c (30.8%), C16:0 (24.1%), and 10-methyl C18:0 (13.9%). The DNA G+C content was 72.0±0.1 mol%. On the basis of phylogenetic and phenotypic differences from members of the genera of the family Nocardioidaceae, a novel genus and species, Mumia flava gen. nov., sp. nov. are proposed. The type strain of Mumia flava is MUSC 201T (=DSM 27763T=MCCC 1A00646T=NBRC 109973T).
The α-amylases from Anoxybacillus species (ASKA and ADTA), Bacillus aquimaris (BaqA) and Geobacillus thermoleovorans (GTA, Pizzo and GtamyII) were proposed as a novel group of the α-amylase family GH13. An ASKA yielding a high percentage of maltose upon its reaction on starch was chosen as a model to study the residues responsible for the biochemical properties. Four residues from conserved sequence regions (CSRs) were thus selected, and the mutants F113V (CSR-I), Y187F and L189I (CSR-II) and A161D (CSR-V) were characterised. Few changes in the optimum reaction temperature and pH were observed for all mutants. Whereas the Y187F (t1/2 43 h) and L189I (t1/2 36 h) mutants had a lower thermostability at 65°C than the native ASKA (t1/2 48 h), the mutants F113V and A161D exhibited an improved t1/2 of 51 h and 53 h, respectively. Among the mutants, only the A161D had a specific activity, k(cat) and k(cat)/K(m) higher (1.23-, 1.17- and 2.88-times, respectively) than the values determined for the ASKA. The replacement of the Ala-161 in the CSR-V with an aspartic acid also caused a significant reduction in the ratio of maltose formed. This finding suggests the Ala-161 may contribute to the high maltose production of the ASKA.
Two novel actinobacteria, strains MUSC 135(T) and MUSC 137, were isolated from mangrove soil at Tanjung Lumpur, Malaysia. The 16S rRNA gene sequence similarity and DNA-DNA relatedness between strains MUSC 135(T) and MUSC 137 were 100 % and 83±3.2 %, confirming that these two strains should be classified in the same species. Strain MUSC 135(T) exhibited a broad-spectrum bacteriocin against the pathogens meticillin-resistant Staphylococcus aureus (MRSA) strain ATCC BAA-44, Salmonella typhi ATCC 19430(T) and Aeromonas hydrophila ATCC 7966(T). A polyphasic approach was used to study the taxonomy of MUSC 135(T), and it showed a range of phylogenetic and chemotaxonomic properties consistent with those of the genus Streptomyces. The diamino acid of the cell-wall peptidoglycan was ll-diaminopimelic acid. The predominant menaquinones were MK-9(H6), MK-9(H4) and MK-9(H8). Polar lipids detected were a lipid, an aminolipid, a phospholipid, phosphatidylinositol, phosphatidylethanolamine and two glycolipids. The predominant cellular fatty acids (>10.0 %) were anteiso-C15 : 0 (20.8 %), iso-C16 : 0 (18.0 %), iso-C15 : 0 (12.2 %) and anteiso-C17 : 0 (11.6 %). The whole-cell sugars were ribose, glucose and mannose. These results suggested that MUSC 135(T) should be placed within the genus Streptomyces. Phylogenetic analysis based on the 16S rRNA gene sequence exhibited that the most closely related strains were Streptomyces cinereospinus NBRC 15397(T) (99.18 % similarity), Streptomyces mexicanus NBRC 100915(T) (99.17 %) and Streptomyces coeruleofuscus NBRC 12757(T) (98.97 %). DNA-DNA relatedness between MUSC 135(T) and closely related type strains ranged from 26.3±2.1 to 49.6±2.5 %. BOX-PCR fingerprint comparisons showed that MUSC 135(T) exhibited a unique DNA profile. The DNA G+C content determined was 70.7±0.3 mol%. Based on our polyphasic study of MUSC 135(T), the strain merits assignment to a novel species, for which the name Streptomyces pluripotens sp. nov. is proposed. The type strain is MUSC 135(T) ( = MCCC 1K00252(T) = DSM 42140(T)).
Strain MUSC 115(T) was isolated from mangrove soil of the Tanjung Lumpur river in the state of Pahang, Peninsular Malaysia. Cells of this strain stained Gram-positive and were non-spore-forming, short rods that formed yellowish-white colonies on different agar media. The taxonomy of strain MUSC 115(T) was studied by a polyphasic approach, and the organism showed a range of phylogenetic and chemotaxonomic properties consistent with those of the genus Microbacterium. The cell-wall peptidoglycan was of type B2β, containing the amino acids ornithine, alanine, glycine, glutamic acid and homoserine. The muramic acid was of the N-glycolyl form. The predominant menaquinones detected were MK-12, MK-13 and MK-11. The polar lipids consisted of phosphatidylglycerol, phosphoglycolipid, diphosphatidylglycerol, two unidentified lipids, three unidentified phospholipids and four unidentified glycolipids. The major fatty acids of the cell membrane were anteiso-C15:0 and anteiso-C17:0. The whole-cell sugars detected were ribose, glucose, mannose and galactose. Based on the 16S rRNA gene sequence, strain MUSC 115(T) showed the highest sequence similarity to Microbacterium immunditiarum SK 18(T) (98.1%), M. ulmi XIL02(T) (97.8%) and M. arborescens DSM 20754(T) (97.5%) and lower sequence similarity to strains of other species of the genus Microbacterium. DNA-DNA hybridization experiments revealed a low level of DNA-DNA relatedness (less than 24%) between strain MUSC 115(T) and the type strains of closely related species. Furthermore, BOX-PCR fingerprint comparison also indicated that strain MUSC 115(T) represented a unique DNA profile. The DNA G+C content determined was 70.9 ± 0.7 mol%, which is lower than that of M. immunditiarum SK 18(T). Based on the combination of genotypic and phenotypic data, it is proposed that strain MUSC 115(T) represents a novel species of the genus Microbacterium, for which the name Microbacterium mangrovi sp. nov. is proposed. The type strain is MUSC 115(T) ( = MCCC 1K00251(T) = DSM 28240(T) = NBRC 110089(T)).
Aeromonas hydrophila is a quorum-sensing (QS) bacterium that causes diarrhea in humans upon infection. Here, we report the genome of pathogenic Aeromonas hydrophila strain 187, which possesses a QS gene responsible for signaling molecule N-acyl homoserine lactone (AHL) synthesis and has been found to be located at contig 36.
Pluralibacter gergoviae FB2, a bacterial strain isolated from packed food, has been found to exhibit quorum-quenching properties. Hence, we report the first, complete genome of P. gergoviae sequenced using the Pacific Biosciences single-molecule, real-time (SMRT) platform.
We previously identified and presented the draft genome of a Xanthomonadaceae bacterial strain Dyella japonica A8 which shows quorum-quenching activity. Here, we report the complete, closed genome sequence of this bacterium. This complete genome may help to further investigate the comparative quorum-quenching activity among D. japonica strains.
A novel HIV-1 recombinant clade (CRF51_01B) was recently identified among men who have sex with men (MSM) in Singapore. As cases of sexually transmitted HIV-1 infection increase concurrently in two socioeconomically intimate countries such as Malaysia and Singapore, cross transmission of HIV-1 between said countries is highly probable. In order to investigate the timeline for the emergence of HIV-1 CRF51_01B in Singapore and its possible introduction into Malaysia, 595 HIV-positive subjects recruited in Kuala Lumpur from 2008 to 2012 were screened. Phylogenetic relationship of 485 amplified polymerase gene sequences was determined through neighbour-joining method. Next, near-full length sequences were amplified for genomic sequences inferred to be CRF51_01B and subjected to further analysis implemented through Bayesian Markov chain Monte Carlo (MCMC) sampling and maximum likelihood methods. Based on the near full length genomes, two isolates formed a phylogenetic cluster with CRF51_01B sequences of Singapore origin, sharing identical recombination structure. Spatial and temporal information from Bayesian MCMC coalescent and maximum likelihood analysis of the protease, gp120 and gp41 genes suggest that Singapore is probably the country of origin of CRF51_01B (as early as in the mid-1990s) and featured a Malaysian who acquired the infection through heterosexual contact as host for its ancestral lineages. CRF51_01B then spread rapidly among the MSM in Singapore and Malaysia. Although the importation of CRF51_01B from Singapore to Malaysia is supported by coalescence analysis, the narrow timeframe of the transmission event indicates a closely linked epidemic. Discrepancies in the estimated divergence times suggest that CRF51_01B may have arisen through multiple recombination events from more than one parental lineage. We report the cross transmission of a novel CRF51_01B lineage between countries that involved different sexual risk groups. Understanding the cross-border transmission of HIV-1 involving sexual networks is crucial for effective intervention strategies in the region.
We report here the complete genome sequence of C. neteri SSMD04, a strain isolated from pickled mackerel sashimi, sequenced by third-generation sequencing technology. To the best of our knowledge, this is the first documentation that reports the complete genome of Cedecea neteri.
N-acylhomoserine lactone (AHL)-based quorum sensing (QS) is important for the regulation of proteobacterial virulence determinants. Thus, the inhibition of AHL synthases offers non-antibiotics-based therapeutic potentials against QS-mediated bacterial infections. In this work, functional AHL synthases of Pseudomonas aeruginosa LasI and RhlI were heterologously expressed in an AHL-negative Escherichia coli followed by assessments on their AHLs production using AHL biosensors and high resolution liquid chromatography-mass spectrometry (LCMS). These AHL-producing E. coli served as tools for screening AHL synthase inhibitors. Based on a campaign of screening synthetic molecules and natural products using our approach, three strongest inhibitors namely are salicylic acid, tannic acid and trans-cinnamaldehyde have been identified. LCMS analysis further confirmed tannic acid and trans-cinnemaldehyde efficiently inhibited AHL production by RhlI. We further demonstrated the application of trans-cinnemaldehyde inhibiting Rhl QS system regulated pyocyanin production in P. aeruginosa up to 42.06%. Molecular docking analysis suggested that trans-cinnemaldehyde binds to the LasI and EsaI with known structures mainly interacting with their substrate binding sites. Our data suggested a new class of QS-inhibiting agents from natural products targeting AHL synthase and provided a potential approach for facilitating the discovery of anti-QS signal synthesis as basis of novel anti-infective approach.
Vibrio parahaemolyticus is a Gram-negative halophilic bacterium that is found in estuarine, marine and coastal environments. V. parahaemolyticus is the leading causal agent of human acute gastroenteritis following the consumption of raw, undercooked, or mishandled marine products. In rare cases, V. parahaemolyticus causes wound infection, ear infection or septicaemia in individuals with pre-existing medical conditions. V. parahaemolyticus has two hemolysins virulence factors that are thermostable direct hemolysin (tdh)-a pore-forming protein that contributes to the invasiveness of the bacterium in humans, and TDH-related hemolysin (trh), which plays a similar role as tdh in the disease pathogenesis. In addition, the bacterium is also encodes for adhesions and type III secretion systems (T3SS1 and T3SS2) to ensure its survival in the environment. This review aims at discussing the V. parahaemolyticus growth and characteristics, pathogenesis, prevalence and advances in molecular identification techniques.
Most Pseudomonas putida strains are environmental microorganisms exhibiting a wide range of metabolic capability but certain strains have been reported as rare opportunistic pathogens and some emerged as multidrug resistant P. putida. This study aimed to assess the drug resistance profile of, via whole genome analysis, P. putida strain T2-2 isolated from oral cavity. At the same time, we also compared the nonenvironmental strain with environmentally isolated P. putida. In silico comparative genome analysis with available reference strains of P. putida shows that T2-2 has lesser gene counts on carbohydrate and aromatic compounds metabolisms, which suggested its little versatility. The detection of its edd gene also suggested T2-2's catabolism of glucose via ED pathway instead of EMP pathway. On the other hand, its drug resistance profile was observed via in silico gene prediction and most of the genes found were in agreement with drug-susceptibility testing in laboratory by automated VITEK 2. In addition, the finding of putative genes of multidrug resistance efflux pump and ATP-binding cassette transporters in this strain suggests a multidrug resistant phenotype. In summary, it is believed that multiple metabolic characteristics and drug resistance in P. putida strain T2-2 helped in its survival in human oral cavity.
Quorum sensing (QS), acts as one of the gene regulatory systems that allow bacteria to regulate their physiological activities by sensing the population density with synchronization of the signaling molecules that they produce. Here, we report a marine isolate, namely strain T47, and its unique AHL profile. Strain T47 was identified using 16S rRNA sequence analysis confirming that it is a member of Vibrio closely clustered to Vibrio sinaloensis. The isolated V. sinaloensis strain T47 was confirmed to produce N-butanoyl-L-homoserine lactone (C4-HSL) by using high resolution liquid chromatography tandem mass spectrometry. V. sinaloensis strain T47 also formed biofilms and its biofilm formation could be affected by anti-QS compound (cathechin) suggesting this is a QS-regulated trait in V. sinaloensis strain T47. To our knowledge, this is the first documentation of AHL and biofilm production in V. sinaloensis strain T47.
Many Proteobacteria communicate via production followed by response of quorum sensing molecules, namely, N-acyl homoserine lactones (AHLs). These molecules consist of a lactone moiety with N-acyl side chain with various chain lengths and degrees of saturation at C-3 position. AHL-dependent QS is often associated with regulation of diverse bacterial phenotypes including the expression of virulence factors. With the use of biosensor and high resolution liquid chromatography tandem mass spectrometry, the AHL production of clinical isolate A. baumannii 4KT was studied. Production of short chain AHL, namely, N-hexanoyl-homoserine lactone (C6-HSL) and N-octanoyl-homoserine lactone (C8-HSL), was detected.