The effect of two different anode-embedding orientations, lengthwise- and widthwise-embedded anodes was explored, on the performance of sediment microbial fuel cells (SMFCs) using a chessboard anode. The maximum current densities and power densities in SMFCs having lengthwise-embedded anodes (SLA1-SLA10) varied from 38.2mA/m(2) to 121mA/m(2) and from 5.5mW/m(2) to 20mW/m(2). In comparison, the maximum current densities and maximum power densities in SMFCs having anodes widthwise-embedded between 0cm to 8cm (SWA2-SWA5) increased from 82mA/m(2) to 140mA/m(2) and from 14.7mW/m(2) to 31.1mW/m(2) as the anode depth became deeper. Although there was a difference in the performance among SWA5-SWA10, it was considered negligible. Hence, it is concluded that it is important to embed anodes widthwise at the specific anode depths, in order to improve of SMFC performance. Chessboard anode used in this work could be a good option for the determination of optimal anode depths.
Microplastic (MP) pollution has emerged as a pressing environmental concern due to its ubiquity and longevity. Biodegradation of MPs has garnered significant attention in combatting global MP contamination. This study focused on MPs within sediments near the sewage outlet of Shenzhen Bay. The objective was to elucidate the microbial communities in sediments with varying MPs, particularly those with high MP loads, and to identify microorganisms associated with MP degradation. The results revealed varying MP abundance, ranging from 211 to 4140 items kg-1 dry weight (d. w.), with the highest concentration observed near the outfall. Metagenomic analysis confirmed the enrichment of Psychrobacter species in sediments with high MP content. Psychrobacter accounted for ∼16.71% of the total bacterial community and 41.71% of hydrocarbon degrading bacteria at the S3 site, exhibiting a higher abundance than at other sampling sites. Psychrobacter contributed significantly to bacterial function at S3, as evidenced by the Kyoto Encyclopedia of Genes and Genomes pathway and enzyme analysis. Notably, 28 enzymes involved in MP biodegradation were identified, predominantly comprising oxidoreductases, hydrolases, transferases, ligases, lyases, and isomerases. We propose a putative mechanism for MP biodegradation, involving the breakdown of long-chain plastic polymers and subsequent oxidation of short-chain oligomers, ultimately leading to thorough mineralization.
In a previous study, notable differences of several physicochemical properties, as well as the community structure of ammonia oxidizing bacteria as judged by 16S rRNA gene analysis, were observed among several disused tin-mining ponds located in the town of Kampar, Malaysia. These variations were associated with the presence of aquatic vegetation as well as past secondary activities that occurred at the ponds. Here, methane oxidizing bacteria (MOB), which are direct participants in the nutrient cycles of aquatic environments and biological indicators of environmental variations, have been characterised via analysis of pmoA functional genes in the same environments. The MOB communities associated with disused tin-mining ponds that were exposed to varying secondary activities were examined in comparison to those in ponds that were left to nature. Comparing the sequence and phylogenetic analysis of the pmoA clone libraries at the different ponds (idle, lotus-cultivated and post-aquaculture), we found pmoA genes indicating the presence of type I and type II MOB at all study sites, but type Ib sequences affiliated with the Methylococcus/Methylocaldum lineage were most ubiquitous (46.7 % of clones). Based on rarefaction analysis and diversity indices, the disused mining pond with lotus culture was observed to harbor the highest richness of MOB. However, varying secondary activity or sample type did not show a strong variation in community patterns as compared to the ammonia oxidizers in our previous study.
The aim of this study was to isolate and identify Actinobacteria from Malaysia mangrove forest and screen them for production of antimicrobial secondary metabolites. Eighty-seven isolates were isolated from soil samples collected at 4 different sites. This is the first report to describe the isolation of Streptomyces, Mycobacterium, Leifsonia, Microbacterium, Sinomonas, Nocardia, Terrabacter, Streptacidiphilus, Micromonospora, Gordonia, and Nocardioides from mangrove in east coast of Malaysia. Of 87 isolates, at least 5 isolates are considered as putative novel taxa. Nine Streptomyces sp. isolates were producing potent antimicrobial secondary metabolites, indicating that Streptomyces isolates are providing high quality metabolites for drug discovery purposes. The discovery of a novel species, Streptomyces pluripotens sp. nov. MUSC 135(T) that produced potent secondary metabolites inhibiting the growth of MRSA, had provided promising metabolites for drug discovery research. The biosynthetic potential of 87 isolates was investigated by the detection of polyketide synthetase (PKS) and nonribosomal polyketide synthetase (NRPS) genes, the hallmarks of secondary metabolites production. Results showed that many isolates were positive for PKS-I (19.5%), PKS-II (42.5%), and NRPS (5.7%) genes, indicating that mangrove Actinobacteria have significant biosynthetic potential. Our results highlighted that mangrove environment represented a rich reservoir for isolation of Actinobacteria, which are potential sources for discovery of antimicrobial secondary metabolites.
A possible tributyltin (TBT)-degrading bacterium isolated from contaminated surface sediment was successfully identified as Klebsiella sp. FIRD 2. It was found to be the best isolate capable of resisting TBT at a concentration of 1000 μg L(-1). This was a concentration above the reported contaminated level at the sampling station, 790 μg L(-1). Further studies revealed that the isolate was Gram negative and resisted TBT concentrations of up to 1500 μg L(-1) in a Minimal Salt Broth without the addition of any carbon source within the first 48 h of incubation. It is expected that additional work could be conducted to check the degradation activity of this new isolate and possibly improve the degradation capacity in order to contribute to finding a safe and sustainable remediation solution of TBT contamination.
To date, the genus Mangrovimonas consists of only one species, Mangrovimonas yunxiaonensis strain LY01 that is known to have algicidal effects against harmful algal blooms (HABs) of Alexandrium tamarense. In this study, the whole genome sequence of three Mangrovimonas-like strains, TPBH4(T)(=LMG 28913(T),=JCM 30882(T)), ST2L12(T)(=LMG 28914(T),=JCM 30880(T)) and ST2L15(T)(=LMG 28915(T),=JCM 30881(T)) isolated from estuarine mangrove sediments in Perak, Malaysia were described. The sequenced genomes had a range of assembly size ranging from 3.56 Mb to 4.15 Mb which are significantly larger than that of M. yunxiaonensis LY01 (2.67 Mb). Xylan, xylose, L-arabinan and L-arabinose utilization genes were found in the genome sequences of the three Mangrovimonas-like strains described in this study. In contrast, these carbohydrate metabolism genes were not found in the genome sequence of LY01. In addition, TPBH4(T) and ST2L12(T) show capability to degrade xylan using qualitative plate assay method.
This study investigates the possible transmission routes of Vibrio spp. in a tropical cage-cultured marine fishes. Samplings of cultured Asian seabass, red snapper, hybrid grouper, wild fish, trash fish, fish fry, water and sediment samples were conducted from December 2016 to August 2017. All fish were dissected in situ and swabs were taken aseptically from the skin, eye, liver and kidney for bacterial isolation and identification. Bacterial isolation and identification from water, sediment and trash fish were also made. A total of 261 Vibrio spp. isolates recovered from the cultured, wild and fry fish, as well as from the sediment and water of the farm environment were analysed. Sequences of the pyrH gene were used to investigate the degree of relatedness and possible transmission routes existing between the isolated Vibrio spp. The population tree revealed the existence of selected Vibrio spp. that possibly transmitted between the newly introduced fish fry and wild fish into the cultured fish, while water also might possibly serves as natural transmission medium of certain Vibrio spp. in this fish farm. SIGNIFICANCE AND IMPACT OF THE STUDY: The source of transmission of Vibrio spp. into farmed marine fish remains unclear. This study highlights the possible transmission routes of Vibrio into cage-cultured marine fishes via newly introduced fish fry and wild fish. Understanding the routes of transmission of Vibrio spp. might help in controlling the disease in the near future.
As the largest genus in Actinobacteria family, Streptomyces species have the ability to synthesize numerous compounds of diverse structures with bioactivities. Streptomyces mangrovisoli MUSC 149T was previously isolated as a novel streptomycete from mangrove forest in east coast of Peninsular Malaysia. The high quality draft genome of MUSC 149T comprises 9,165,825bp with G+C content of 72.5%. Through bioinformatics analysis, 21 gene clusters identified in the genome were associated with the production of bioactive secondary metabolites. The presence of these biosynthetic gene clusters in MUSC 149T suggests the potential exploitation of the strain for production of medically important compounds.
The continuous accumulation of microplastics in the environment poses ecological threats and has been an increasing problem worldwide. In this study, eight bacterial strains were isolated from mangrove sediment in Peninsular Malaysia to mitigate the environmental impact of microplastics and develop a clean-up option. The bacterial isolates were screened for their potential to degrade UV-treated microplastics from polyethylene (PE), polyethylene terephthalate (PET), polypropylene (PP), and polystyrene (PS). Only two isolates, namely, Bacillus cereus and Bacillus gottheilii, grew on a synthetic medium containing different microplastic polymers as the sole carbon source. A shake flask experiment was carried out to further evaluate the biodegradability potential of the isolates. Degradation was monitored by recording the weight loss of microplastics and the growth pattern of the isolates in the mineral medium. The biodegradation extent was validated by assessment of the morphological and structural changes through scanning electron microscopy and Fourier transform infrared spectroscopy analyses. The calculated weight loss percentages of the microplastic particles by B. cereus after 40 days were 1.6%, 6.6%, and 7.4% for PE, PET, and PS, respectively. B. gottheilii recorded weight loss percentages of 6.2%, 3.0%, 3.6%, and 5.8% for PE, PET, PP, and PS, respectively. The designated isolates degraded the microplastic material and exhibited potential for remediation of microplastic-contaminated environment. Biodegradation tests must be conducted to characterize the varied responses of microbes toward pollutants, such as microplastics. Hence, a novel approach for biodegradation of microplastics must be developed to help mitigate the environmental impact of plastics and microplastic polymers.
Resting strategies of planktonic organisms are important for the ecological processes of coastal waters and their impacts should be taken into consideration in management of water bodies used by multiple industries. We combined different approaches to evaluate the importance of resting stages in Singapore coastal waters. We used molecular approaches to improve the knowledge on Singapore biodiversity, we sampled and extracted cysts from sediments to evaluate the density of resting stages in Johor Strait, and we compared systematically information on Singapore planktonic biodiversity to existing published information on resting stages from these reported organisms. This is the first study evaluating the importance of resting stages in Singapore waters. Above 120 species reported in Singapore are known to produce resting stages though no previous work has ever been done to evaluate the importance of these strategies in these waters. The results from the resting stage survey confirmed 0.66 to 5.34 cyst g-1 dry weight sediment were present in the Johor Strait suggesting that cysts may be flushed by tidal currents into and out of the strait regularly. This also suggest that the blooms occurring in Singapore are likely due to secondary growth of Harmful Algae Bloom species in the water rather than from direct germination of cysts from sediment. Finally, we discuss the importance of these resting eggs for three main national industries in Singapore (shipping, marine aquaculture and provision of drinking water through seawater desalination). We argue that this study will serve as a baseline for some of the future management of Singapore waters.
Interest in the biodegradation of microplastics is due to their ubiquitous distribution, availability, high persistence in the environment and deleterious impact on marine biota. The present study evaluates the growth response and mechanism of polypropylene (PP) degradation by Bacillus sp. strain 27 and Rhodococcus sp. strain 36 isolated from mangrove sediments upon exposure to PP microplastics. Both bacteria strains were able to utilise PP microplastic for growth as confirmed by the reduction of the polymer mass. The weight loss was 6.4% by Rhodococcus sp. strain 36 and 4.0% by Bacillus sp. strain 27 after 40days of incubation. PP biodegradation was further confirmed using Fourier-transform infrared spectroscopy and scanning electron microscopy analyses, which revealed structural and morphological changes in the PP microplastics with microbial treatment. These analyses showed that the isolates can colonise, modify and utilise PP microplastics as carbon source.
Benzo[a]pyrene is a high-molecular-weight polycyclic aromatic hydrocarbon highly recalcitrant in nature and thus harms the ecosystem and/or human health. Therefore, its removal from the marine environment is crucial. This research focuses on benzo[a]pyrene degradation by using enriched bacterial isolates in consortium under saline conditions. Bacterial isolates capable of using benzo[a]pyrene as sole source of carbon and energy were isolated from enriched mangrove sediment. These isolates were identified as Ochrobactrum anthropi, Stenotrophomonas acidaminiphila, and Aeromonas salmonicida ss salmonicida. Isolated O. anthropi and S. acidaminiphila degraded 26% and 20%, respectively, of an initial benzo[a]pyrene concentration of 20 mg/L after 8 days of incubation in seawater (28 ppm of NaCl). Meanwhile, the bacterial consortium decomposed 41% of an initial 50 mg/L benzo[a]pyrene concentration after 8 days of incubation in seawater (28 ppm of NaCl). The degradation efficiency of benzo[a]pyrene increased to 54%, when phenanthrene was supplemented as a co-metabolic substrate. The order of biodegradation rate by temperature was 30°C > 25°C > 35°C. Our results suggest that co-metabolism by the consortium could be a promising biodegradation strategy for benzo[a]pyrene in seawater.
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)).
This study for the first time provides insight into the bacterial community in the benthic region of the Off-Terengganu Coastline, which is considered to be anthropogenically polluted due to heavy fishing vessel commotion. Subsurface bacteria were randomly collected from two locations at different depths and were examined using the 16S rDNA V3-V4 marker gene on the Illumina™ Miseq platform. In addition, the physiochemical parameters of the sediment were also measured. Surprisingly, the results show a high diversity of sulfur-oxidizing bacteria in the surveyed area, where Sulfurovum sp. was identified to predominate the overall bacterial community. The physiochemical parameters reveal insufficient evidence of hydrothermal vents in the surveyed area. However, there are traces of hydrocarbon pollutants such as gasoline, diesel, and mineral oil in this area. It is assumed that sediment accumulation in the lee of breakwater plays an important role in trapping the runoff from the nearby harbor, which includes oil spills. Based on the common knowledge, Sulvurofum sp. is a native bacterium that exists in deep hydrothermal vents and volcanic territories. Although the reason for the abundance of Sulfurovum sp. in the surveyed area is still unclear, there is a possibility that metabolic adaptation plays an important role in regulating hydrocarbon pollutants for survival. The work presented in this paper therefore has profound implications for future studies on Sulfurovum sp. versatility. However, future research is needed to strengthen the findings of this study and to provide a better evidence regarding the metabolic response of this bacterium toward hydrocarbon pollutants.
Tropical peat swamp forests are important and endangered ecosystems, although little is known of their microbial diversity and ecology. We used molecular and enzymatic techniques to examine patterns in prokaryotic community structure and overall microbial activity at 0-, 10-, 20-, and 50-cm depths in sediments in a peat swamp forest in Malaysia. Denaturing gradient gel electrophoresis profiles of amplified 16S ribosomal ribonucleic acid (rRNA) gene fragments showed that different depths harbored different bacterial assemblages and that Archaea appeared to be limited to the deeper samples. Cloning and sequencing of longer 16S rRNA gene fragments suggested reduced microbial diversity in the deeper samples compared to the surface. Bacterial clone libraries were largely dominated by ribotypes affiliated with the Acidobacteria, which accounted for at least 27-54% of the sequences obtained. All of the sequenced representatives from the archaeal clone libraries were Crenarchaeota. Activities of microbial extracellular enzymes involved in carbon, nitrogen, and phosphorus cycling declined appreciably with depth, the only exception being peroxidase. These results show that tropical peat swamp forests are unusual systems with microbial assemblages dominated by members of the Acidobacteria and Crenarchaeota. Microbial communities show clear changes with depth, and most microbial activity is likely confined to populations in the upper few centimeters, the site of new leaf litter fall, rather than the deeper, older, peat layers.
The present study aimed to determine the degradation and transformation of three-ring PAHs phenanthrene and anthracene by Cryptococcus sp. MR22 and Halomonas sp. BR04 under halophilic conditions. The growth progress of Cryptococcus sp. MR22 and Halomonas sp. BR04 on anthracene and phenanthrene was monitored by colony-forming unit (CFU) technique. The growth of the bacteria was maintained at a maximum concentration of 200 mg/L of all tested hydrocarbon, indicating that Cryptococcus sp. MR22 and Halomonas sp. BR04 significantly perform in the removal of the PAH-contaminated medium at low concentrations. The fit model to represent the biodegradation kinetics of both PAHs was first-order rate equation The extract prepared from cells supplemented with three different substrates exhibited some enzymes such as hydroxylase, dioxygenase, laccase and peroxidase. The results suggest that both strains had an impressive ability in the degradation of aromatic and aliphatic hydrocarbon but also could tolerate in the extreme salinity condition.
Klebsiella pneumoniae is an opportunistic pathogen that is responsible for causing nosocomial and community-acquired infections. Despite its common presence in soil and aquatic environments, the virulence potential of K. pneumoniae isolates of environmental origin is largely unknown. Hence, in this study, K. pneumoniae isolated from the estuarine waters and sediments of the Matang mangrove estuary were screened for potential virulence characteristics: antibiotic susceptibility, morphotype on Congo red agar, biofilm formation, presence of exopolysaccharide and capsule, possession of virulence genes (fimH, magA, ugE, wabG and rmpA) and their genomic fingerprints. A total of 55 strains of K. pneumoniae were isolated from both human-distributed sites (located along Sangga Besar River) and control sites (located along Selinsing River) where less human activity was observed, indicated that K. pneumoniae is ubiquitous in the environment. However, the detection of potentially virulent strains at the downstream of Kuala Sepetang village has suggested an anthropogenic contamination source. In conclusion, the findings from this study indicate that the Matang mangrove estuary could harbor potentially pathogenic K. pneumoniae with risk to public health. More studies are required to compare the environmental K. pneumoniae strains with the community-acquired K. pneumoniae strains.
A Gram-staining-negative, aerobic, rod-shaped, yellow-orange-pigmented, gliding bacterium, designated as strain ST2L12(T), was isolated from estuarine mangrove sediment from Matang Mangrove Forest, Perak, Malaysia. Strain ST2L12(T) grew at 15-39 °C, pH 6-8 and in 1-6 % (w/v) NaCl. This strain was able to degrade xylan and casein. 16S rRNA gene sequence analysis showed 95.3-92.8 % similarity to members of the genera Mangrovimonas, Meridianimaribacter, Sediminibacter, Gaetbulibacter and Hoppeia. Phylogenetic analysis indicated that it belonged to the family Flavobacteriaceae. Respiratory quinone present was menaquinone-6 (MK-6), and the DNA G+C content was 38.3 mol%. The predominant fatty acids were iso-C15:0, iso-C15:1, C15:0 and iso-C17:0 3-OH. Moreover, previous genome comparison study showed that the genome of ST2L12(T) is 1.4 times larger compared to its closest relative, Mangrovimonas yunxiaonensis LYYY01(T). Phenotypic, fatty acid, 16S rRNA gene sequence and previous genome data indicate that strain ST2L12(T) represents a novel species of the genus Mangrovimonas in the family Flavobacteriaceae, for which the name Mangrovimonas xylaniphaga sp. nov. is proposed. The type strain of Mangrovimonas xylaniphaga is ST2L12(T) (=LMG 28914(T)=JCM 30880(T)).
A novel, rod-shaped, Gram-stain-negative, halophilic and non-motile bacterium, designated CCB-MM1T, was isolated from a sample of estuarine sediment collected from Matang Mangrove Forest, Malaysia. The cells possessed a rod-coccus cell cycle in association with growth phase and formed aggregates. Strain CCB-MM1T was both catalase and oxidase positive, and able to degrade starch. Optimum growth occurred at 30 °C and pH 7.0 in the presence of 2-3 % (w/v) NaCl. The 16S rRNA gene sequence of strain CCB-MM1T showed 98.12, 97.46 and 97.33 % sequence similarity with Microbulbifer rhizosphaerae Cs16bT, Microbulbifer maritimus TF-17T and Microbulbifergwangyangensis GY2T respectively. Strain CCB-MM1T and M. rhizosphaerae Cs16bT formed a cluster in the phylogenetic tree. The major cellular fatty acids were iso-C17 : 1 ω9c and iso-C15 : 0, and the total polar lipid profile consisted of phosphatidylglycerol, phosphatidylethanolamine, phosphoaminolipid, two unidentified lipids, an unidentified glycolipid and an unidentified aminolipid. The major respiratory quinone was ubiquinone Q-8 and the genomic DNA G+C content of the strain was 58.9 mol%. On the basis of the phylogenetic, phenotypic and genotypic data presented here, strain CCB-MM1T represents a novel species of the genus Microbulbifer, for which the name Microbulbiferaggregans sp. nov. is proposed. The type strain is CCB-MM1T (=LMG 29920T=JCM 31875T).
Tioman Island is one of many sources for underexplored actinobacterial diversity in Malaysia. Selective isolation, molecular profiling, 16S rRNA gene sequencing and phylogenetic analyses were carried out to highlight the diversity of the marine actinobacterial community in a sediment collected off Tioman Island. A high number of diverse actinobacteria were recovered using skim milk/HEPES pre-treatment on a mannitol-based medium. A total of 123 actinobacterial strains were isolated, including thirty obligate marine actinobacteria putatively identified as Salinispora spp. Molecular fingerprinting profiles obtained with a double digestion approach grouped the remaining non-Salinispora-like strains into 24 different clusters, with Streptomyces and Blastococcus as the major clusters. A total of 17 strains were identified as novel actinobacterial species within the genera Streptomyces (n = 6), Blastococcus (n = 5), Marinactinospora (n = 3), Nocardiopsis (n = 1), Agromyces (n = 1) and Nonomuraea (n = 1) based on 16S rRNA gene sequence analyses. Polyphasic data from three putative Marinactinospora spp. showed that the strains represent a new genus in the Nocardiopsaceae family. Crude extracts from the strains were also found to inhibit the growth of Gram-positive (Staphylococcus aureus, Bacillus subtilis) and Gram-negative (Providencia alcalifaciens) pathogens. Hierarchical clustering of the bioactivities of an active fraction revealed a unique profile, which is closely related that of fosfomycin.