Marine genomics最新文献

During an attempt to screen secondary metabolites of pharmaceutical utility, we sequenced the complete genome of type strain of a novel marine bacterial genus, named genus Hyphococcus. The type strain, Hyphococcus flavus MCCC 1K03223^T, was isolated from bathypelagic seawater of South China Sea at a depth of 2500 m. The complete genome of strain MCCC 1K03223^T is composed of a circular chromosome of 3,472,649 bp with a mean G + C content of 54.8%. Functional genomic analysis showed that this genome encodes five biosynthetic gene clusters, which were annotated to synthesize medicinally important secondary metabolites. Secondary metabolites annotated include ectoine which acts cytoprotection, ravidomycin which is an antitumor antibiotic and three other different metabolites of terpene type. The secondary metabolic potentials of H. flavus revealed in this study provide more evidences on mining bioactive substances from marine bathypelagic microorganisms.

Nudibranchs are colorful marine invertebrates having a diverse group of understudied animals. Recently, some nudibranch members have acquired some attention while others still have not. Chromodoris quadricolor is a member of the Red Sea nudibranch, which did not have the chance to get significant attention. Unlike various invertebrates, it lacks a shell suggesting that it must defend itself in other ways. Therefore, in the present study, we were concerned about the mantle-associated bacterial communities. Being essential partners of this dorid nudibranch system, we investigated their taxonomic and functional profiles. We performed a whole metagenomic shotgun approach for the mantle bacterial cells after a differential pelleting procedure. In this procedure, we separated most of the prokaryotic cells from the eukaryotic host cells. Our findings showed that the mantle-body part holds a diverse group of bacterial species relating mainly to Proteobacteria and Tenericutes phyla. There were novel findings regarding the bacterial members associated with the nudibranch mollusks group. Various species were not previously recorded as bacterial symbionts with nudibranchs. Those members were Bathymodiolus brooksi thiotrophic gill symbiont (23.2%), Mycoplasma marinum (7.4%), Mycoplasma todarodis (5%), and Solemya velum gill symbiont (2.6%). The presence of these bacterial species assumed a nutritional role to the host. However, some of these species were present in a high abundance, suggesting their important symbiosis with Chromodoris quadricolor. In addition, exploring the bacterial ability to produce valuable products resulted in the prediction of 2088 biosynthetic gene clusters (BGCs). We identified different gene cluster classes. Polyketide BGC class was the most represented. Others were related to fatty acid BGCs, RiPP, saccharide, terpene, and NRP BGC classes. Prediction of the activity of these gene clusters resulted in, mainly, an antibacterial activity. In addition, different antimicrobial secondary metabolites were also detected. These secondary metabolites are considered key components regulating the bacterial species interactions in their ecosystem. This suggested the significant contribution of these bacterial symbionts to protect the nudibranch host against predators and pathogens. Globally, it is the first detailed study concerned with both the taxonomic diversity and functional potentials of the bacterial symbionts associated with Chromodoris quadricolor mantle.

Bacillus cereus 2-6A, was isolated from the sediments in the hydrothermal area of the Pacific Ocean with a water depth of 2628 m. In this study, we report the whole genome sequence of strain 2-6A and analyze that to understand its metabolic capacities and biosynthesis potential of natural products. The genome of strain 2-6A consists of a circular chromosome of 5,191,018 bp with a GC content of 35.3 mol% and two plasmids of 234,719 bp and 411,441 bp, respectively. Genomic data mining reveals that strain 2-6A has several gene clusters involved in exopolysaccharides (EPSs) and polyhydroxyalkanoates (PHAs) production and complex polysaccharides degradation. It also possesses a variety of genes for allowing strain 2-6A to cope with osmotic stress, oxidative stress, heat shock, cold shock and heavy metal stress, which could play a vital role in the adaptability of the strain to hydrothermal environments. Gene clusters for secondary metabolite production, such as lasso peptide and siderophore, are also predicted. Therefore, genome sequencing and data mining provide insights into the molecular mechanisms of Bacillus in adapting to hydrothermal deep ocean environments and can facilitate further experimental exploration.

Herein, we report the complete genome sequence of Pseudoalteromonas sp. PS1M3 (= NCBI 87791), which is a psychrotrophic bacterium that inhabits in seabed off the Boso Peninsula, Japan Trench. Analysis of the genomic sequence revealed that PS1M3 possesses 2 circular chromosomal DNAs and 2 circular plasmid DNAs. The genome of PS1M3 had a total size of 4,351,630 bp, an average GC content of 39.9%, and contained a total of 3811 predicted protein coding sequences, 28 rRNAs, and 100 tRNAs. The Kyoto Encyclopedia of Genes and Genomes (KEGG) was utilized to annotate the genes and KofamKOALA within KEGG assigned a gene cluster involved in glycogen biosynthesis and metabolic pathways with regard to heavy metal resistance (copper; cop and mercury; mer), indicating that PS1M3 can potentially use a stored glycogen as an energy source under oligotrophic environment and cope with multi-heavy metal contamination. To assess available genome relatedness indices, whole-genome average nucleotide identity analysis was examined using the complete genome sequences of Pseudoalteromonas spp., showing that 67.29–97.40% sequence similarity with PS1M3. This study may be useful in understanding the roles of a psychrotrophic Pseudoalteromonas in cold deep-sea sediment adaptation mechanisms.

Mycolicibacterium phocaicum RL-HY01, a marine bacterial strain with the capability to degrade phthalic acid esters (PAEs), was isolated from Zhanjiang Bay, China. Here, the complete genome sequence of strain RL-HY01 was presented. The genome of strain RL-HY01 contains one circular chromosome of 6,064,759 bp with a G + C content of 66.93 mol%. The genome contains 5681 predicted protein-encoding genes, 57 tRNA genes, and 6 rRNA genes. Genes and gene clusters potentially involved in the metabolism of PAEs were further identified. The genome Mycolicibacterium phocaicum RL-HY01 will be helpful for advancing our understanding of the fate of PAEs in marine ecosystem.

Marine algicidal bacteria and their metabolites are considered to be one of the most effective strategies to mitigate the harmful algal blooms (HABs). The bacterium Hahella sp. KA22 has previously been confirmed to have strong algicidal activity against the HABs causing microalgae, Heterosigma akashiwo. In this study, the molecular mechanism of microalgae cell death was detected. The results showed that the cell growth rate and photosynthetic efficiency were inhibited with addition of algicidal strain KA22, while the accumulation of reactive oxygen species (ROS) and oxidative damage in H. akashiwo cells increased. A total of 2056 unigenes were recognized to be differentially expressed in transcriptome sequences. In particular, the transcriptional levels of light-harvesting pigments and structural proteins in the oxygen-evolving-complex were continuously down-regulated, corresponding to the significant reduction of photosynthetic efficiency and the accumulation of ROS. Furthermore, glutamate dehydrogenase was significantly up-regulated in abundance. Meanwhile, calcium-dependent protein kinases were also detected with significant changes. Collectively, algicidal stress caused the suppressed electron transfer in chloroplast and impaired detoxification of intracellular oxidants by glutathione, which may subsequently result in multiple cell regulation and metabolic responses and ultimately lead to the ROS-dependent cell death of H. akashiwo.

Members of the genus Pseudomonas have been frequently isolated from the marine environment, indicating their ecological role in native habitats. One bacterial strain, Pseudomonas sp. BSw22131, was isolated from seawater in Kongsfjorden, Svalbard. The bacterium can grow with algae-derived dimethylsulfoniopropionate (DMSP) as the sole carbon source. Here, we sequenced the complete genome of strain BSw22131, which contained a single circular chromosome of 5,739,290 (G + C content of 58.23 mol%) without any plasmids. A total of 5362 protein-coding genes, 65 tRNA genes, and 16 rRNA genes were obtained. Genome sequence analysis revealed that strain BSw22131 was not only a potential novel species of the genus Pseudomonas but also different from Pseudomonas sp. DMSP-1 that was isolated from the same habitat and also utilized DMSP as the sole carbon source for growth. The results can be helpful for understanding the catabolism of the genus Pseudomonas in sulfur cycling in the Arctic fjord ecosystem.

Many secondary metabolites with medicinal potential are produced by various animals, plants, and microorganisms. Because marine creatures have a greater proportion of unexplored biodiversity than their terrestrial counterparts, they have emerged as a key research focus for the discovery of natural product drugs. Several studies have revealed that bacteria isolated from Chromodoris quadricolor (C. quadricolor) have antibiotic and anticancer properties. In this study, meta-transcriptomics and meta-proteimic analysis were combined to identify biosynthetic gene clusters (BGCs) in the symbiotic bacteria of the C. quadricolor mantle. Symbiotic bacteria were separated from the host by differential pelleting, and then total RNA was extracted, purified, and sequenced. Meta-transcriptomic analysis was done using different natural product mining tools to identify biosynthetic transcript clusters (BTCs). Furthermore, proteins were extracted from the same cells and then analyzed by LC-MS. A meta-proteomic analysis was performed to find proteins that are translated from BCGs. Finally, only 227 proteins have been translated from 40,742 BTCs. The majority of these clusters were polyketide synthases (PKSs) with antibacterial activity. Ten novel potential metabolic clusters with the ability to produce antibiotics have been identified in Novosphingobium and Microbacteriaceae, including members of the ribosomal synthesized and post-translationally modified peptides (RiPPs), polyketide synthases, and others. We realized that using a meta-proteomic approach to identify BGCs that have already been translated makes it easier to concentrate on BGCs that are utilized by bacteria. The symbiotic bacteria associated with C. quadricolor could be a source of novel antibiotics.

Bacillus subtilis TY-1 was isolated from 2000 m-deep sea sediments of the Western Pacific Ocean, which was found to exhibit strong antagonistic activity against tobacco bacterial wilt caused by Ralstonia solanacearum. Here, we present the annotated complete genomic sequence of the strain Bacillus subtilis TY-1. The genome consists of a 4,030,869-bp circular chromosome with a G + C content of 43.88%, 86 tRNAs, and 30 rRNAs. Genomic analysis identified a large number of gene clusters involved in the biosynthesis of antibacterial metabolites, including lipopeptides(surfactin, bacillibactin, and fengycin) and polyketides(bacillaene). Meanwhile, numerous genes encoding carbohydrate-active enzymes and secreted proteins were found in TY-1. These findings suggest that Bacillus subtilis TY-1 appears to be a potential biocontrol agent against tobacco bacterial wilt in agricultural fields.

Marinimicrobium sp. C6131, which had the ability to degrade chitin, was isolated from deep-sea sediment of the southwest Indian Ocean. Here, the genome of strain C6131 was sequenced and the chitin metabolic pathways were constructed. The genome contained a circular chromosome of 4,207,651 bp with a G + C content of 58.50%. A total of 3471 protein-coding sequences were predicted. Gene annotation and metabolic pathway reconstruction showed that strain C6131 possessed genes and two metabolic pathways involved in chitin catabolism: the hydrolytic chitin utilization pathway initiated by chitinases and the oxidative chitin utilization pathway initiated by lytic polysaccharide monooxygenases. Chitin is the most abundant polysaccharide in the ocean. Degradation and recycling of chitin driven by marine bacteria are crucial for biogeochemical cycles of carbon and nitrogen in the ocean. The genomic information of strain C6131 revealed its genetic potential involved in chitin metabolism. The strain C6131 could grow with colloidal chitin as the sole carbon source, indicating that these genes would have functions in chitin degradation and utilization. The genomic sequence of Marinimicrobium sp. C6131 could provide fundamental information for future studies on chitin degradation, and help to improve our understanding of the chitin degradation process in deep-sea environments.