Microbulbifer taiwanensis sp. nov., isolated from coastal soil

Sub-lethal concentration of sulfamethoxazole affects the growth performance of milkfish (Chanos chanos), the microbial composition of antibiotic-resistant bacteria and the prevalence of sulfonamide-resistance genes in mariculture

To investigate the impacts of sub-lethal concentrations of antibiotic agents in mariculture, culturable approach and DNA based detection were employed to isolate and analyse resistant bacteria and resistant genes in this study. Milkfish (Chanos chanos), the target rearing animal was exposed to sulfamethoxazole (SMX; 2 mg/L) for 8 weeks and resulted in reduced survival rate and weight gain to 61.9 % and 28.4 %, respectively compared to control milkfish (p < 0.001). The composition of SMX-resistant bacteria isolated from the culture water and the gastrointestinal tracts of milkfish underwent changes in response to SMX treatment with a reduced diversity. The prevalence of SMX resistant genes sul in bacterial isolates was elevated from 2.8 % of control to 100 % of SMX-administrated water. Exposure to SMX at a sub-lethal dosage enhanced the prevalence of resistance genes sul1 and sul2 in resistant bacteria, thus implying high frequency of resistance dissemination in the marine environment and surrounding ecosystems.

Microbulbifer okhotskensis sp. nov., isolated from a deep bottom sediment of the Okhotsk Sea

A Gram-negative, aerobic, non-motile bacterium КMM 9862^T was isolated from a deep bottom sediment sample obtained from the Okhotsk Sea, Russia. Based on the 16S rRNA gene and whole genome sequences analyses the novel strain КMM 9862^T fell into the genus Microbulbifer (class Gammaproteobacteria) sharing the highest 16S rRNA gene sequence similarities of 97.4% to Microbulbifer echini AM134^T and Microbulbifer epialgicus F-104^T, 97.3% to Microbulbifer pacificus SPO729^T, 97.1% to Microbulbifer variabilis ATCC 700307^T, and similarity values of < 97.1% to other recognized Microbulbifer species. The average nucleotide identity and digital DNA-DNA hybridization values between strain КMM 9862^T and M. variabilis ATCC 700307^T and M. thermotolerans DSM 19189^T were 80.34 and 77.72%, and 20.2 and 19.0%, respectively. Strain КMM 9862^T contained Q-8 as the predominant ubiquinone and C_16:0, C_16:1 ω7c, C_12:0, and C_10:0 3-OH as the major fatty acids. The polar lipids were phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, phosphatidylcholine, an unidentified aminophospholipid, an unidentified aminolipid, two unidentified phospholipids, phosphatidic acid, and an unidentified lipid. The DNA G+C content of 49.8% was calculated from the genome sequence. On the basis of the phylogenetic evidence and distinctive phenotypic characteristics, the marine bacterium KMM 9862^T is proposed to be classified as a novel species Microbulbifer okhotskensis sp. nov. The type strain of the species is strain KMM 9862^T (= KACC 22804^T).

Novel Polyhydroxybutyrate-Degrading Activity of the Microbulbifer Genus as Confirmed by Microbulbifer sp. SOL03 from the Marine Environment

Ever since bioplastics were globally introduced to a wide range of industries, the disposal of used products made with bioplastics has become an issue inseparable from their application. Unlike petroleum-based plastics, bioplastics can be completely decomposed into water and carbon dioxide by microorganisms in a relatively short time, which is an advantage. However, there is little information on the specific degraders and accelerating factors for biodegradation. To elucidate a new strain for biodegrading poly-3-hydroxybutyrate (PHB), we screened out one PHB-degrading bacterium, Microbulbifer sp. SOL03, which is the first reported strain from the Microbulbifer genus to show PHB degradation activity, although Microbulbifer species are known to be complex carbohydrate degraders found in high-salt environments. In this study, we evaluated its biodegradability using solid- and liquid-based methods in addition to examining the changes in physical properties throughout the biodegradation process. Furthermore, we established the optimal conditions for biodegradation with respect to temperature, salt concentration, and additional carbon and nitrogen sources; accordingly, a temperature of 37°C with the addition of 3% NaCl without additional carbon sources, was determined to be optimal. In summary, we found that Microbulbifer sp. SOL03 showed a PHB degradation yield of almost 97% after 10 days. To the best of our knowledge, this is the first study to investigate the potent bioplastic degradation activity of Microbulbifer sp., and we believe that it can contribute to the development of bioplastics from application to disposal.

Complete genome sequence of Microbulbifer sp. YPW1 from mangrove sediments in Yanpu harbor, China

In this work, a strain named YPW1 was isolated from the sediments of an artificial mangrove in Yanpu harbor, China. A complete genome of YPW1 was sequenced and assembled. The 16S rRNA gene assigned strain YPW1 into genus Microbulbifer, and the maximum values of average nucleotide identity and digital DNA-DNA hybridization of ZHDP1 genome were 90.36 and 68.1, respectively, indicating that YPW1 was a potential new species in genus Microbulbifer. A total of 10 representative genomes from genus Microbulbifer were selected to compare with YPW1. The results showed that the genome of strain YPW1 possessed more carbohydrate-active enzyme genes to transform various recalcitrant polysaccharides into bioavailable monosaccharides than those of the selected genomes. Furthermore, among the selected genomes, YPW1 was the only strain with nitrate, nitrite, and nitric oxide reductases which could appoint nitrous oxide, a powerful greenhouse gas, as the end-product of its denitrification process. Therefore, strain YPW1 was a potential novel member of genus Microbulbifer with special ecological roles in the cycles of carbon and nitrogen in mangrove ecosystems.

Microbulbifer hainanensis sp. nov., a moderately halopilic bacterium isolated from mangrove sediment

A new bacterium was successfully isolated from a mangrove sediment sample in Haikou City, Hainan Province, China. The organism is a Gram-negative, rod-shaped, non-motile and strictly aerobic bacterium, named NBU-8HK146^T. Strain NBU-8HK146^T was able to grow at temperatures of 10-40 °C, at salinities of 0-11% (w/v) and at pH 5.5-9.5. Veoges-Proskauer, methyl red reaction and hydrolysis of Tween 20 were negative. Catalase and oxidase activities, H₂S production, hydrolysis of starch, casein, Tweens 40, 60 and 80 were positive. The major cellular fatty acids were C_16:0, iso-C_15:0 and summed feature 9. The major respiratory quinone was ubiquinone-8 (Q-8). The major polar lipids were phosphatidylethanolamine, phosphatidylglycerol and two unidentified glycolipids. According to 16S rRNA gene sequence similarities, strain NBU-8HK146^T shared 98.0%, 97.9%, 97.7%, 97.6% and 97.3% similarities to the species with validated name Microbulbifer taiwanensis CC-LN1-12^T, Microbulbifer rhizosphaerae Cs16b^T, Microbulbifer marinus Y215^T, Microbulbifer donghaiensis CN85^T and Microbulbifer aggregans CCB-MM1^T, respectively. Phylogenetic analyses indicated that strain NBU-8HK146^T formed a distinct lineage with strains Microbulbifer taiwanensis CC-LN1-12^T and Microbulbifer marinus Y215^T. Both digital DNA-DNA hybridization values (19.5-22.7%) and average nucleotide identity values (73.2-78.9%) between strain NBU-8HK146^T and related species of genus Microbulbifer were below the species delineation cutoffs. The DNA G+C content was 58.9 mol%. Many proteins involving in the adaption of osmotic stress in the salt environment of mangrove were predicted in genome of strain NBU-8HK146^T. From phenotypic, genotypic, phylogenetic and chemotaxonomic characteristics, strain NBU-8HK146^T can be regarded as a new Microbulbifer species for which the name Microbulbifer hainanensis. The type strain is NBU-8HK146^T (= KCTC 82226^T = MCCC 1K04737^T).

Microbulbifer harenosus sp. nov., an alginate-degrading bacterium isolated from coastal sand

A Gram-stain-negative, aerobic, rod-shaped bacterium with peritrichous flagella, designated strain HB161719^T, was isolated from coastal sand collected from Tanmen Port in Hainan, PR China. The isolate was found to grow with 2-11 % (w/v) NaCl, at 15-45 °C and pH 6.0-10.0, with an optima of 2-3 % NaCl, 37 °C and pH 7.0, respectively. Chemotaxonomic analysis showed that Q-8 was detected as the sole respiratory quinone and that iso-C_15 : 0 and summed features 3, 8 and 9 were the major cellular fatty acids. The G+C content of the genomic DNA was 58.2 mol%. Analysis of the 16S rRNA gene sequence of the strain showed an affiliation with the genus Microbulbifer, sharing 98.7, 98.4, 97.8 and 97.8 % sequence similarities to the closest relatives of Microbulbifer okinawensis ABABA23^T, Microbulbifer pacificus SPO729^T, Microbulbifer taiwanensis CC-LN1-12^T and Microbulbifer gwangyangensis GY2^T, respectively. Low DNA-DNA hybridization values showed that it formed a distinct genomic species. The combined phenotypic and molecular features supported that strain HB161719^T represents a novel species of the genus Microbulbifer, for which the name Microbulbifer harenosus sp. nov. is proposed. The type strain is HB161719^T (=CGMCC 1.13584^T=JCM 32688^T).

Complete genome sequence of Microbulbifer sp. CCB-MM1, a halophile isolated from Matang Mangrove Forest, Malaysia

Microbulbifer sp. CCB-MM1 is a halophile isolated from estuarine sediment of Matang Mangrove Forest, Malaysia. Based on 16S rRNA gene sequence analysis, strain CCB-MM1 is a potentially new species of genus Microbulbifer. Here we describe its features and present its complete genome sequence with annotation. The genome sequence is 3.86 Mb in size with GC content of 58.85%, harbouring 3313 protein coding genes and 92 RNA genes. A total of 71 genes associated with carbohydrate active enzymes were found using dbCAN. Ectoine biosynthetic genes, ectABC operon and ask_ect were detected using antiSMASH 3.0. Cell shape determination genes, mreBCD operon, rodA and rodZ were annotated, congruent with the rod-coccus cell cycle of the strain CCB-MM1. In addition, putative mreBCD operon regulatory gene, bolA was detected, which might be associated with the regulation of rod-coccus cell cycle observed from the strain.

A taxonomic framework for emerging groups of ecologically important marine gammaproteobacteria based on the reconstruction of evolutionary relationships using genome-scale data

In recent years a large number of isolates were obtained from saline environments that are phylogenetically related to distinct clades of oligotrophic marine gammaproteobacteria, which were originally identified in seawater samples using cultivation independent methods and are characterized by high seasonal abundances in coastal environments. To date a sound taxonomic framework for the classification of these ecologically important isolates and related species in accordance with their evolutionary relationships is missing. In this study we demonstrate that a reliable allocation of members of the oligotrophic marine gammaproteobacteria (OMG) group and related species to higher taxonomic ranks is possible by phylogenetic analyses of whole proteomes but also of the RNA polymerase beta subunit, whereas phylogenetic reconstructions based on 16S rRNA genes alone resulted in unstable tree topologies with only insignificant bootstrap support. The identified clades could be correlated with distinct phenotypic traits illustrating an adaptation to common environmental factors in their evolutionary history. Genome wide gene-content analyses revealed the existence of two distinct ecological guilds within the analyzed lineage of marine gammaproteobacteria which can be distinguished by their trophic strategies. Based on our results a novel order within the class Gammaproteobacteria is proposed, which is designated Cellvibrionales ord. nov. and comprises the five novel families Cellvibrionaceae fam. nov., Halieaceae fam. nov., Microbulbiferaceae fam. nov., Porticoccaceae fam. nov., and Spongiibacteraceae fam. nov.

Microbulbifer gwangyangensis sp. nov. and Microbulbifer pacificus sp. nov., isolated from marine environments

Two novel Gram-stain-negative, chemoheterotrophic and strictly aerobic bacteria, strains GY2T and SPO729T, were isolated from a tidal flat at Gwangyang Bay in Korea and a marine sponge sample from the Pacific Ocean, respectively. The two strains were halotolerant, catalase- and oxidase-positive, and non-motile rods. Optimum temperature and pH for growth of both strains were observed to be 35 °C and pH 7.0–7.5, but optimum salinity for strain SPO729T [2–3 % (w/v)] was slightly higher than that for strain GY2T (1–2 %). The major cellular fatty acids of both strains were C16 : 0, iso-C15 : 0, iso-C17 : 0, iso-C17 : 1ω9c, C18 : 1ω7c, iso-C11 : 0 and iso-C11 : 0 3-OH. The genomic DNA G+C contents of strains GY2T and SPO729T were 55.1 and 57.9 mol%, respectively, and ubiquinone 8 (Q-8) was detected as the sole respiratory quinone from the two strains. Phylogenetic analysis based on 16S rRNA gene sequences showed that strains GY2T and SPO729T formed tight phyletic lineages with members of the genus Microbulbifer . Strain GY2T was closely related to Microbulbifer okinawensis ABABA23T (98.2 %), strain SPO729T (98.0 %) and Microbulbifer donghaiensis CN85T (97.0 %); strain SPO729T was closely related to M. okinawensis ABABA23T (98.3 %) and M. donghaiensis CN85T (98.2 %). The DNA–DNA relatedness values of strain GY2T with M. okinawensis ABABA23T, strain SPO729T and M. donghaiensis CN85T were 40.0±2.1 %, 13.1±3.9 % and 16.2±5.8 %, respectively, whereas those of strain SPO729T with M. okinawensis ABABA23T and M. donghaiensis CN85T were 48.0±4.0 % and 34.6±9.3 %, respectively. On the basis of phenotypic and molecular features, it is concluded that the two strains GY2T and SPO729T represent two novel species of the genus Microbulbifer , for which the names Microbulbifer gwangyangensis sp. nov. and Microbulbifer pacificus are proposed; the type strains are GY2T ( = KACC 16189T = JCM 17800T) and SPO729T ( = KCCM 42667T = JCM 14507T), respectively.