Psychrobacter fjordensis sp. nov., a psychrotolerant bacterium isolated from an Arctic fjord in Svalbard

Psychrobacter Phage Encoding an Antibiotics Resistance Gene Represents a Novel Caudoviral Family

Psychrobacter is an important bacterial genus that is widespread in Antarctic and marine environments. However, to date, only two complete Psychrobacter phage sequences have been deposited in the NCBI database. Here, the novel Psychrobacter phage vB_PmaS_Y8A, infecting Psychrobacter HM08A, was isolated from sewage in the Qingdao area, China. The morphology of vB_PmaS_Y8A was characterized by transmission electron microscopy, revealing an icosahedral head and long tail. The genomic sequence of vB_PmaS_Y8A is linear, double-stranded DNA with a length of 40,226 bp and 44.1% G+C content, and encodes 69 putative open reading frames. Two auxiliary metabolic genes (AMGs) were identified, encoding phosphoadenosine phosphosulfate reductase and MarR protein. The first AMG uses thioredoxin as an electron donor for the reduction of phosphoadenosine phosphosulfate to phosphoadenosine phosphate. MarR regulates multiple antibiotic resistance mechanisms in Escherichia coli and is rarely found in viruses. No tRNA genes were identified and no lysogeny-related feature genes were detected. However, many similar open reading frames (ORFs) were found in the host genome, which may indicate that Y8A also has a lysogenic stage. Phylogenetic analysis based on the amino acid sequences of whole genomes and comparative genomic analysis indicate that vB_PmaS_Y8A contains a novel genomic architecture similar only to that of Psychrobacter phage pOW20-A, although at a low similarity. vB_PmaS_Y8A represents a new family-level virus cluster with 22 metagenomic assembled viral genomes, here named Minviridae. IMPORTANCE Although Psychrobacter is a well-known and important bacterial genus that is widespread in Antarctic and marine environments, genetic characterization of its phages is still rare. This study describes a novel Psychrobacter phage containing an uncharacterized antibiotic resistance gene and representing a new virus family, Minviridae. The characterization provided here will bolster current understanding of genomes, diversity, evolution, and phage-host interactions in Psychrobacter populations.

Psychrobacter halodurans sp. nov. and Psychrobacter coccoides sp. nov., two new slightly halophilic bacteria isolated from marine sediment

In this study, two bacterial strains designated F2608T and F1192T, isolated from marine sediment sampled in Weihai, PR China, were characterized using a polyphasic approach. Strains were aerobic, Gram-stain-negative and motile. According to the results of phylogenetic analyses based on their 16S rRNA genes, these two strains should be classified under the genus Psychrobacter and they both show <98.5% sequence similarity to their closest relative, Psychrobacter celer JCM 12601T. Moreover, strain F2608T showed 97.5% sequence similarity to strain F1192T. Strain F2608T grew at 4–37 °C (optimum, 30–33 °C) and at pH 6.0–9.0 (optimum, pH 6.5–7.0) in the presence of 0–12% (w/v) NaCl (optimum, 4.0–5.0%). Strain F1192T grew at 4–37 °C (optimum, 30 °C) and at pH 5.5–9.0 (optimum, pH 7.0–7.5) in the presence of 0.5–12% (w/v) NaCl (optimum, 3.0–4.0%). The genomic DNA G+C contents of strain F2608T and strain F1192T were 47.4 and 44.9 %, respectively. Genomic characteristics including average nucleotide identity and digital DNA–DNA hybridization values clearly separated strain F2608T from strain F1192T. The sole isoprenoid quinone in these two strains was ubiquinone 8 and the major cellular fatty acids (>10.0%) were C18:1 ω9c and C17:1 ω8c. The major polar lipids of these two strains were phosphatidylglycerol, phosphatidylethanolamine and diphosphatidylglycerol. Based on the results of polyphasic analysis, the two strains represent two novel species of the genus Psychrobacter , for which the names Psychrobacter halodurans sp. nov. and Psychrobacter coccoides sp. nov. are proposed. The type strains are F2608T (=MCCC 1K05774T=KCTC 82766T) and F1192T (=MCCC 1K05775T=KCTC 82765T), respectively.

Comparative Study of the Gut Microbiota Among Four Different Marine Mammals in an Aquarium

Despite an increasing appreciation in the importance of host–microbe interactions in ecological and evolutionary processes, information on the gut microbial communities of some marine mammals is still lacking. Moreover, whether diet, environment, or host phylogeny has the greatest impact on microbial community structure is still unknown. To fill part of this knowledge gap, we exploited a natural experiment provided by an aquarium with belugas (Delphinapterus leucas) affiliated with family Monodontidae, Pacific white-sided dolphins (Lagenorhynchus obliquidens) and common bottlenose dolphin (Tursiops truncatus) affiliated with family Delphinidae, and Cape fur seals (Arctocephalus pusillus pusillus) affiliated with family Otariidae. Results show significant differences in microbial community composition of whales, dolphins, and fur seals and indicate that host phylogeny (family level) plays the most important role in shaping the microbial communities, rather than food and environment. In general, the gut microbial communities of dolphins had significantly lower diversity compared to that of whales and fur seals. Overall, the gut microbial communities were mainly composed of Firmicutes and Gammaproteobacteria, together with some from Bacteroidetes, Fusobacteria, and Epsilonbacteraeota. However, specific bacterial lineages were differentially distributed among the marine mammal groups. For instance, Lachnospiraceae, Ruminococcaceae, and Peptostreptococcaceae were the dominant bacterial lineages in the gut of belugas, while for Cape fur seals, Moraxellaceae and Bacteroidaceae were the main bacterial lineages. Moreover, gut microbial communities in both Pacific white-sided dolphins and common bottlenose dolphins were dominated by a number of pathogenic bacteria, including Clostridium perfringens, Vibrio fluvialis, and Morganella morganii, reflecting the poor health condition of these animals. Although there is a growing recognition of the role microorganisms play in the gut of marine mammals, current knowledge about these microbial communities is still severely lacking. Large-scale research studies should be undertaken to reveal the roles played by the gut microbiota of different marine mammal species.

Genome sequence of three Psychrobacter sp. strains with potential applications in bioremediation

To date, the genus Psychrobacter consists of 37 recognized species isolated from different sources, however they are more frequently found in cold and other non-polar environments of low water activity. Some strains belonging to the genus have shown different enzymatic activities with potential applications in bioremediation or food industry. In the present study, the whole genome sequences of three Psychrobacter-like strains (C 20.9, Cmf 22.2 and Rd 27.2) isolated from reared clams in Galicia (Spain) are described. The sequenced genomes resulted in an assembly size of 3,143,782 bp for C 20.9 isolate, 3,168,467 bp for Cmf 22.2 isolate and 3,028,386 bp for Rd 27.2 isolate. Among the identified coding sequences of the genomes, mercury detoxification and biogeochemistry genes were found, as well as genes related to heavy metals and antibiotic resistance. Also virulence-related features were identified such as the siderophore vibrioferrin or an aerobactin-like siderophore. The phylogenetic analysis of the 16S rRNA gene suggested that these strains may represent novel species of the Psychrobacter genus. The genome sequences of the Psychrobacter sp. strains have been deposited at DDBJ/EMBL/GenBank under the accession numbers MRYA00000000 (Cmf 22.2), MRYB00000000 (Rd 27.2) and MRYC00000000 (C 20.9), and the sequences could be found at the site https://www.ncbi.nlm.nih.gov/bioproject/PRJNA353858.