Pseudoalteromonas arctica sp. nov., an aerobic, psychrotolerant, marine bacterium isolated from Spitzbergen

Computational Insight into Intraspecies Distinctions in Pseudoalteromonas distincta: Carotenoid-like Synthesis Traits and Genomic Heterogeneity

Advances in the computational annotation of genomes and the predictive potential of current metabolic models, based on more than thousands of experimental phenotypes, allow them to be applied to identify the diversity of metabolic pathways at the level of ecophysiology differentiation within taxa and to predict phenotypes, secondary metabolites, host-associated interactions, survivability, and biochemical productivity under proposed environmental conditions. The significantly distinctive phenotypes of members of the marine bacterial species Pseudoalteromonas distincta and an inability to use common molecular markers make their identification within the genus Pseudoalteromonas and prediction of their biotechnology potential impossible without genome-scale analysis and metabolic reconstruction. A new strain, KMM 6257, of a carotenoid-like phenotype, isolated from a deep-habituating starfish, emended the description of P. distincta, particularly in the temperature growth range from 4 to 37 °C. The taxonomic status of all available closely related species was elucidated by phylogenomics. P. distincta possesses putative methylerythritol phosphate pathway II and 4,4'-diapolycopenedioate biosynthesis, related to C30 carotenoids, and their functional analogues, aryl polyene biosynthetic gene clusters (BGC). However, the yellow-orange pigmentation phenotypes in some strains coincide with the presence of a hybrid BGC encoding for aryl polyene esterified with resorcinol. The alginate degradation and glycosylated immunosuppressant production, similar to brasilicardin, streptorubin, and nucleocidines, are the common predicted features. Starch, agar, carrageenan, xylose, lignin-derived compound degradation, polysaccharide, folate, and cobalamin biosynthesis are all strain-specific.

Bioprospecting for Novel Bacterial Sources of Hydrolytic Enzymes and Antimicrobials in the Romanian Littoral Zone of the Black Sea

Marine microorganisms have evolved a large variety of metabolites and biochemical processes, providing great opportunities for biotechnologies. In the search for new hydrolytic enzymes and antimicrobial compounds with enhanced characteristics, the current study explored the diversity of cultured and uncultured marine bacteria in Black Sea water from two locations along the Romanian coastline. Microbial cell density in the investigated samples varied between 65 and 12.7 × 10³ CFU·mL^-1. The total bacterial community identified by Illumina sequencing of 16S rRNA gene comprised 185 genera belonging to 46 classes, mainly Gammaproteobacteria, Alphaproteobacteria, Flavobacteriia, and 24 phyla. The 66 bacterial strains isolated on seawater-based culture media belonged to 33 genera and showed variable growth temperatures, growth rates, and salt tolerance. A great fraction of these strains, including Pseudoalteromonas and Flavobacterium species, produced extracellular proteases, lipases, and carbohydrases, while two strains belonging to the genera Aquimarina and Streptomyces exhibited antimicrobial activity against human pathogenic bacteria. This study led to a broader view on the diversity of microbial communities in the Black Sea, and provided new marine strains with hydrolytic and antimicrobial capabilities that may be exploited in industrial and pharmaceutical applications.

Identification and Characterization of Three Chitinases with Potential in Direct Conversion of Crystalline Chitin into N,N′-diacetylchitobiose

Chitooligosaccharides (COSs) have been widely used in agriculture, medicine, cosmetics, and foods, which are commonly prepared from chitin with chitinases. So far, while most COSs are prepared from colloidal chitin, chitinases used in preparing COSs directly from natural crystalline chitin are less reported. Here, we characterize three chitinases, which were identified from the marine bacterium Pseudoalteromonas flavipulchra DSM 14401^T, with an ability to degrade crystalline chitin into (GlcNAc)₂ (N,N’-diacetylchitobiose). Strain DSM 14401 can degrade the crystalline α-chitin in the medium to provide nutrients for growth. Genome and secretome analyses indicate that this strain secretes six chitinolytic enzymes, among which chitinases Chia4287, Chib0431, and Chib0434 have higher abundance than the others, suggesting their importance in crystalline α-chitin degradation. These three chitinases were heterologously expressed, purified, and characterized. They are all active on crystalline α-chitin, with temperature optima of 45–50 °C and pH optima of 7.0–7.5. They are all stable at 40 °C and in the pH range of 5.0–11.0. Moreover, they all have excellent salt tolerance, retaining more than 92% activity after incubation in 5 M NaCl for 10 h at 4 °C. When acting on crystalline α-chitin, the main products of the three chitinases are all (GlcNAc)₂, which suggests that chitinases Chia4287, Chib0431, and Chib0434 likely have potential in direct conversion of crystalline chitin into (GlcNAc)₂.

Pseudoalteromonas ostreae sp. nov., a new bacterial species harboured by the flat oyster Ostrea edulis

Three bacterial strains, named hOe-66^T, hOe-124 and hOe-125, were isolated from the haemolymph of different specimens of the flat oyster Ostrea edulis collected in Concarneau bay (Finistère, France). These strains were characterized by a polyphasic approach, including (i) whole genome analyses with 16S rRNA gene sequence alignment and pangenome analysis, determination of the G+C content, average nucleotide identity (ANI), and in silico DNA-DNA hybridization (isDDH), and (ii) fatty acid methyl ester and other phenotypic analyses. Strains hOe-66^T, hOe-124 and hOe-125 were closely related to both type strains Pseudoalteromonas rhizosphaerae RA15^T and Pseudoalteromonas neustonica PAMC 28425^T with less than 93.3% ANI and 52.3% isDDH values. Regarding their phenotypic traits, the three strains were Gram-negative, 1-2 µm rod-shaped, aerobic, motile and non-spore-forming bacteria. Cells grew optimally at 25 °C in 2.5% NaCl and at 7-8 pH. The most abundant fatty acids were summed feature 3 (C_16:1 ω7c/C_16:1 ω6c), C_16:0 and C_17:1 ω8c. The strains carried a genome average size of 4.64 Mb and a G+C content of 40.28 mol%. The genetic and phenotypic results suggested that strains hOe-66^T, hOe-124 and hOe-125 belong to a new species of the genus Pseudoalteromonas. In this context, we propose the name Pseudoalteromonas ostreae sp. nov. The type strain is hOe-66^T (=CECT 30303^T=CIP 111911^T).

Degradation and Utilization of Alginate by Marine Pseudoalteromonas: a Review

Alginate, which is mainly produced by brown algae and decomposed by heterotrophic bacteria, is an important marine organic carbon source. The genus Pseudoalteromonas contains diverse forms of heterotrophic bacteria that are widely distributed in marine environments and are an important group in alginate degradation. In this review, the diversity of alginate-degrading Pseudoalteromonas is introduced, and the characteristics of Pseudoalteromonas alginate lyases, including their sequences, enzymatic properties, structures, and catalytic mechanisms, and the synergistic effect of Pseudoalteromonas alginate lyases on alginate degradation are introduced. The acquisition of the alginate degradation capacity and the alginate utilization pathways of Pseudoalteromonas are also introduced. This paper provides a comprehensive overview of alginate degradation by Pseudoalteromonas, which will contribute to the understanding of the degradation and recycling of marine algal polysaccharides driven by marine bacteria.

Taxonomic and Enzymatic Characterization of Flocculibacter collagenilyticus gen. nov., sp. nov., a Novel Gammaproteobacterium With High Collagenase Production

Collagens from marine animals are an important component of marine organic nitrogen. Collagenase-producing bacteria and their collagenases play important roles in collagen degradation and organic nitrogen recycling in the ocean. However, only a few collagenase-producing marine bacteria have been so far discovered. Here, we reported the isolation and characterization of a collagenase-secreting bacterium, designated strain SM1988^T, isolated from a green alga Codium fragile sample. Strain SM1988^T is a Gram-negative, aerobic, oxidase-, and catalase-positive, unipolar flagellated, and rod-shaped bacterium capable of hydrolyzing casein, gelatin and collagens. Phylogenetic analysis revealed that strain SM1988^T formed a distinct phylogenetic lineage along with known genera within the family Pseudoalteromonadaceae, with 16S rRNA gene sequence similarity being less than 93.3% to all known species in the family. Based on the phylogenetic, genomic, chemotaxonomic and phenotypic data, strain SM1988^T was considered to represent a novel species in a novel genus in the family Pseudoalteromonadaceae, for which the name Flocculibacter collagenilyticus gen. nov., sp. nov. is proposed, with the type strain being SM1988^T (= MCCC 1K04279^T = KCTC 72761^T). Strain SM1988^T showed a high production of extracellular collagenases, which had high activity against both bovine collagen and codfish collagen. Biochemical tests combined with genome and secretome analyses indicated that the collagenases secreted by strain SM1988^T are serine proteases from the MEROPS S8 family. These data suggest that strain SM1988^T acts as an important player in marine collagen degradation and recycling and may have a promising potential in collagen resource utilization.

Pseudoalteromonas caenipelagi sp. nov., isolated from a tidal flat

A Gram-stain-negative, aerobic, non-spore-forming, motile by single polar flagellum and ovoid or rod-shaped bacterial strain, designated JBTF-M23^T, was isolated from tidal flat sediment collected from the Yellow Sea, Republic of Korea. Neighbour-joining phylogenetic tree of 16S rRNA gene sequences showed that strain JBTF-M23^T fell within the clade comprising the type strains of Pseudoalteromonas species, clustering with the type strains of P. byunsanensis and P. amylolytica. Strain JBTF-M23^T exhibited the highest 16S rRNA gene sequence similarity value (98.6 %) to the type strain of P. rubra and sequence similarities of 98.3 and 97.7 % to the type strains of P. byunsanensis and P. amylolytica, respectively. The DNA G+C content of strain JBTF-M23^T from genomic sequence data was 41.98 %. The ANI and dDDH values between strain JBTF-M23^T and the type strains of P. rubra, P. byunsanensis and P. amylolytica were 71.3-76.6 and 19.4-19.9 %, respectively. Strain JBTF-M23^T contained Q-8 as the predominant ubiquinone and C_16 : 1  ω7c and/or C_16 : 1  ω6c, C_16 : 0 and C_18 : 1  ω7c as the major fatty acids. The major polar lipids of strain JBTF-M23^T were phosphatidylethanolamine and one unidentified aminolipid. Distinguished phenotypic properties, along with the phylogenetic and genetic distinctiveness, revealed that strain JBTF-M23^T is separated from recognized Pseudoalteromonas species. On the basis of the data presented, strain JBTF-M23^Tis considered to represent a novel species of the genus Pseudoalteromonas, for which the name Pseudoalteromonas caenipelagi sp. nov. is proposed. The type strain is JBTF-M23^T(=KACC 19900^T=NBRC 113647^T).

Marine Bacterial Esterases: Emerging Biocatalysts for Industrial Applications

The marine ecosystem has been known to be a significant source of novel enzymes. Esterase enzymes (EC 3.1.1.1) represent a diverse group of hydrolases that catalyze the cleavage and formation of ester bonds. Although esterases are widely distributed among marine organisms, only microbial esterases are of paramount industrial importance. This article discusses the importance of marine microbial esterases, their biochemical and kinetic properties, and their stability under extreme conditions. Since culture-dependent techniques provide limited insights into microbial diversity of the marine ecosystem, therefore, genomics and metagenomics approaches have widely been adopted in search of novel esterases. Additionally, the article also explains industrial applications of marine bacterial esterases particularly for the synthesis of optically pure substances, the preparation of enantiomerically pure drugs, the degradation of human-made plastics and organophosphorus compounds, degradation of the lipophilic components of the ink, and production of short-chain flavor esters.

Impact of Bio-Carrier Immobilized with Marine Bacteria on Self-Healing Performance of Cement-Based Materials

The present study evaluated the self-healing efficiency and mechanical properties of mortar specimens incorporating a bio-carrier as a self-healing agent. The bio-carrier was produced by immobilizing ureolytic bacteria isolated from seawater in bottom ash, followed by surface coating with cement powder to prevent loss of nutrients during the mixing process. Five types of specimens were prepared with two methods of incorporating bacteria, and were water cured for 28 days. To investigate the healing ratio, the specimens with predefined cracks were treated by applying a wet–dry cycle in three different conditions, i.e., seawater, tap water, and air for 28 days. In addition, a compression test and a mercury intrusion porosimetry analysis of the specimens were performed to evaluate their physico-mechanical properties. The obtained results showed that the specimen incorporating the bio-carrier had higher compressive strength than the specimen incorporating vegetative cells. Furthermore, the highest healing ratio was observed in specimens incorporating the bio-carrier. This phenomenon could be ascribed by the enhanced bacterial viability by the bio-carrier.

Multipartite genomes and the sRNome in response to temperature stress of an Arctic Pseudoalteromonas fuliginea BSW20308

Little is known about the survival and effect of rapid climate warming on Pseudoalteromonas in the Arctic, although it is abundant and important in this ecosystem. Here, we investigated a cold-adapted Pseudoalteromonas fuliginea BSW20308 from the Arctic Ocean, from the genome to its transcriptomic responses towards temperature changes. It contained two circular chromosomes, with the second chromosome probably evolved from an ancestral plasmid. The evolution of multipartite genomes may be advantageous for its survival under changing environments. RNA-seq analysis revealed the extensive involvement of sRNome in response to temperature stress for the first time, especially tmRNA and a novel Pf1 sRNA strongly induced under heat stress. The present study makes significant contributions towards the understanding of Pseudoalteromonas in two aspects: the genome structure and evolution of its two chromosomes, and the important discovery of the sRNome in response to temperature stress.

Motilimonas eburnea gen. nov., sp. nov., isolated from coastal sediment

A novel Gram-stain-negative, non-spore-forming, facultatively anaerobic bacterium, designated YH6T, was isolated from marine sediment in Weihai, China. Cells of starin YH6T were motile, straight rods that formed ivory-white colonies on 2216E agar. Optimal growth occurred at 28-33 °C (range 15-37 °C), in the presence of 2-4 % (w/v) NaCl (range 1-8 %) and at pH 7.5-8.5 (range pH 6.5-9.0). The sole respiratory lipoquinone was Q-8, and the major fatty acids (>10 %) were C16 : 0 and summed feature 3 (C16 : 1ω7c/iso-C15 : 0 2-OH). The polar lipids profile of the novel strain consisted of phosphatidylglycerol, phosphatidylethanolamine, diphosphatidylglycerol and several other unknown lipids (phospholipids, lipid and phosphoaminolipid). The G+C content of the genomic DNA was 46.5 mol%. The closest type strain phylogenetically to strain YH6T was Vibrio variabilis (92.99 % 16S rRNA gene sequence similarity) followed by Paramoritella alkaliphila (92.55 %), Pseudoalteromonas aurantia (92.20 %) and Pseudoalteromonas citrea (92.20 %). Phylogenetic analysis of the 16S rRNA gene sequence placed the novel strain in the order Alteromonadales, class Gammaproteobacteria. On the basis of the 16S rRNA gene sequence data as well as physiological and biochemical characteristics, we concluded that strain YH6T represents a novel species of a new genus. We propose the name of Motilimonas eburnea gen. nov., sp. nov. for this novel species. The type strain of the novel species is YH6T (=KCTC 42594T=MCCC 1H00122T).

Pseudoalteromonas gelatinilytica sp. nov., isolated from surface seawater

Three Gram-stain-negative, rod-shaped bacteria, designated strains NH153T, F-2-11 and M-1-78, were isolated from surface seawater of the South China Sea and the East China Sea. The three isolates were able to grow at 15-45 °C (optimum 28-37 °C), but no growth occurred at 4 or 50 °C. The pH range for growth was pH 5.5-9.5 (optimum pH 7.5-8.5). The isolates required sea salts for growth and growth occurred in the presence of 0-10 % (w/v) NaCl (optimum 3-5 %); no growth occurred in the presence of 12.0, 15.0 or 20.0 % (w/v) NaCl. They were positive for hydrolysis of gelatin and Tween 80. The sole respiratory quinone was ubiquinone-8 (Q-8). The major cellular fatty acids (>10 %) were C16 : 0, C18 : 1ω7c and summed feature 3 (C16 : 1ω7c and/or iso-C15 : 0 2-OH). The major polar lipid components were phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, one unidentified glycolipid, one unidentified phospholipid and one unidentified lipid. The genomic DNA G+C content of strain NH153T was 41.4 mol%. Based on 16S rRNA gene sequence analysis, the isolates were closely related to the type strain of Pseudoalteromonas shioyasakiensis (98.0-98.6 % sequence similarity). The 16S rRNA gene sequence similarities between the three isolates were 98.8-99.7 %. Phylogenetic analysis indicated that they formed a distinct lineage and clustered with P. shioyasakiensis and Pseudoalteromonas arabiensis. The level of DNA-DNA relatedness among the three isolates was 78.0-85.5 %. Strain NH153T exhibited average nucleotide identity values of 93.4 and 84.2 % with respect to P. shioyasakiensisJCM 18891T and P. arabiensisJCM 17292T, respectively. The genome-to-genome distance analysis revealed that strain NH153T shared 52.4 % DNA relatedness with P. shioyasakiensisJCM 18891T and 28.1 % with P. arabiensisJCM 17292T. On the basis of the phenotypic, genotypic and chemotaxonomic characterizations, as well as phylogenetic inference obtained in this study, strains NH153T, F-2-11 and M-1-78 represent a novel species within the genus Pseudoalteromonas, for which the name Pseudoalteromonasgelatinilytica sp. nov. is proposed. The type strain is NH153T (=CGMCC 1.15370T=DSM 100951T), and F-2-11 (=CGMCC 1.15364=DSM 100953) and M-1-78 (=CGMCC 1.15365=DSM 100952), are additional strains of the species.

Pseudoalteromonas fenneropenaei sp. nov., a marine bacterium isolated from sediment of a Fenneropenaeus chinensis pond

A novel Gram-stain-negative, motile, oxidase- and catalase-positive, non-spore-forming, non-pigmented, aerobic bacterium, designated rzy34^T, was isolated from the sediment of a pond containing farmed Fenneropenaeus chinensis Rizhao, China. The strain was able to grow at pH 6-10 (optimum pH 7), 20-40 °C (optimum 30 °C) and in the presence of 1.0-6.0 % NaCl (optimum 1.0-2.0 %). Phylogenetic analysis based on 16S rRNA gene sequences revealed that the nearest relative of strain rzy34^T was Pseudoalteromonas xiamenensis Y2^T, with the highest sequence similarity of 96.09 %. Within the genus Pseudoalteromonas, it showed the lowest similarity of 92.7 % to Pseudoalteromonas donghaensis. The G+C content of the chromosomal DNA of strain rzy34^T was 45.3 mol%. The predominant cellular fatty acids were summed feature 3 (C16 : 1ω6c and/or C16 : 1ω7c), C16 : 0, C17 : 1ω8c and summed feature 8 (C18 : 1ω6c and/or C18 : 1ω7c). The major respiratory quinone was Q-8. Polar lipid analysis indicated the presence of phosphatidylethanolamine and phosphatidylcholine. On the basis of the phenotypic and phylogenetic characteristics, strain rzy34^T represents a novel species of the genus Pseudoalteromonas, for which the name Pseudoalteromonas fenneropenaei sp. nov. is proposed. The type strain is rzy34^T (=CGMCC 1.15325^T=KCTC 42730^T).

Draft Genome Sequence of Pseudoalteromonas sp. Strain A2, an Isolate with High Antioxidative Activity from Arctic Seawater

Here we report the draft genome sequence of Pseudoalteromonas strain A2, isolated from Arctic seawater in the pack-ice zone, which has high antioxidative activity against H 2 O 2 . The genomics information of this strain will facilitate the study of antioxidative mechanisms, cold adaptation properties, and evolution of this genus.

Pseudoalteromonas xiamenensis sp. nov., a marine bacterium isolated from coastal surface seawater

A Gram-negative, oxidase- and catalase-positive, rod-shaped, non-spore-forming, motile, aerobic bacterium, designated Y2(T), was isolated from surface seawater of Yundang Lake, Xiamen, China. The strain was able to grow in the presence of 0.5-6.0% NaCl (optimum 1.0-1.5%), at pH 5-10 (optimum pH 8) and at 10-40 °C (optimum 25 °C). Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain Y2(T) belongs to the genus Pseudoalteromonas, with the highest sequence similarity of 94.9% to Pseudoalteromonas tunicata D2(T); within the genus Pseudoalteromonas, it showed the lowest similarity of 92.8% to Pseudoalteromonas denitrificans ATCC 43337(T). The G+C content of the chromosomal DNA of strain Y2(T) was 45.1 mol%. The predominant fatty acids were summed feature 3 (C(16 : 1)ω6c and/or C(16 : 1)ω7c), C(16 : 0), C(12 : 0) 3-OH and summed feature 8 (C(18 : 1)ω6c and/or C(18 : 1)ω7c). The only respiratory quinone detected was Q-8. Based on the phylogenetic and phenotypic characteristics, strain Y2(T) represents a novel species of the genus Pseudoalteromonas, for which the name Pseudoalteromonas xiamenensis sp. nov. is proposed; the type strain is Y2(T) ( = CGMCC 1.12157(T) = JCM 18779(T)).

Pseudoalteromonas xishaensis sp. nov., isolated from Acanthaster planci in the Xisha islands

A Gram-negative, aerobic, motile by means of single polar flagellum, short rod-shaped marine bacterium, designated strain E418T, was isolated from the spines on the body surface of starfish Acanthaster planci in the Xisha islands, China. Cells of strain E418T were found to grow optimally at pH 7–8, at 25–37 °C, and in the presence of 2–5 % (w/v) NaCl. Phylogenetic analysis based on the comparison of 16S rRNA gene sequences revealed that strain E418T is a member of the genus Pseudoalteromonas. The closest relative to this strain was found to be P. ruthenica LMG 19699T, with a similarity level of 97.7 %. DNA relatedness between the novel isolate and this phylogenetically related species was 57.4 %. Strain E418T decomposed Tween 80, gelatin, and casein, but was unable to decompose starch and grow on DNase Agar. The cellular fatty acid profile consisted of significant amounts of C16:1ω7c/C16:1ω6c, C18:1ω7c/C18:1ω6c, C16:0, and C17:1ω8c. The G+C content of DNA of this strain was determined to be 46.7 mol%. Phenotypic characteristics, phylogenetic analysis and DNA–DNA relatedness data suggest that strain E418T represents a novel species of the genus Pseudoalteromonas, for which the name Pseudoalteromonas xishaensis sp. nov. is proposed. The type strain of P. xishaensis is strain E418T (DSM 25588T = NBRC 108846T = CCTCC AB 2011177T).

Microbe observation and cultivation array (MOCA) for cultivating and analyzing environmental microbiota

BACKGROUND

The use of culture-independent nucleic acid techniques, such as ribosomal RNA gene cloning library analysis, has unveiled the tremendous microbial diversity that exists in natural environments. In sharp contrast to this great achievement is the current difficulty in cultivating the majority of bacterial species or phylotypes revealed by molecular approaches. Although recent new technologies such as metagenomics and metatranscriptomics can provide more functionality information about the microbial communities, it is still important to develop the capacity to isolate and cultivate individual microbial species or strains in order to gain a better understanding of microbial physiology and to apply isolates for various biotechnological applications.

RESULTS

We have developed a new system to cultivate bacteria in an array of droplets. The key component of the system is the microbe observation and cultivation array (MOCA), which consists of a Petri dish that contains an array of droplets as cultivation chambers. MOCA exploits the dominance of surface tension in small amounts of liquid to spontaneously trap cells in well-defined droplets on hydrophilic patterns. During cultivation, the growth of the bacterial cells across the droplet array can be monitored using an automated microscope, which can produce a real-time record of the growth. When bacterial cells grow to a visible microcolony level in the system, they can be transferred using a micropipette for further cultivation or analysis.

CONCLUSIONS

MOCA is a flexible system that is easy to set up, and provides the sensitivity to monitor growth of single bacterial cells. It is a cost-efficient technical platform for bioassay screening and for cultivation and isolation of bacteria from natural environments.

Genome sequences of six Pseudoalteromonas strains isolated from Arctic sea ice

Yu et al. (Polar Biol. 32:1539-1547, 2009) isolated 199 Pseudoalteromonas strains from Arctic sea ice. We sequenced the genomes of six of these strains, which are affiliated to different Pseudoalteromonas species based on 16S rRNA gene sequences, facilitating the study of physiology and adaptation of Arctic sea ice Pseudoalteromonas strains.

A cold-adapted esterase of a novel marine isolate, Pseudoalteromonas arctica: gene cloning, enzyme purification and characterization

A gene encoding an esterase (estO) was identified and sequenced from a gene library screen of the psychrotolerant bacterium Pseudoalteromonas arctica. Analysis of the 1,203 bp coding region revealed that the deduced peptide sequence is composed of 400 amino acids with a predicted molecular mass of 44.1 kDa. EstO contains a N-terminal esterase domain and an additional OsmC domain at the C-terminus (osmotically induced family of proteins). The highly conserved five-residue motif typical for all alpha/beta hydrolases (G x S x G) was detected from position 104 to 108 together with a putative catalytic triad consisting of Ser(106), Asp(196), and His(225). Sequence comparison showed that EstO exhibits 90% amino acid identity with hypothetical proteins containing similar esterase and OsmC domains but only around 10% identity to the amino acid sequences of known esterases. EstO variants with and without the OsmC domain were produced and purified as His-tag fusion proteins in E. coli. EstO displayed an optimum pH of 7.5 and optimum temperature of 25 degrees C with more than 50% retained activity at the freezing point of water. The thermostability of EstO (50% activity after 5 h at 40 degrees C) dramatically increased in the truncated variant (50% activity after 2.5 h at 90 degrees C). Furthermore, the esterase displays broad substrate specificity for esters of short-chain fatty acids (C(2)-C(8)).

Pseudoalteromonas lipolytica sp. nov., isolated from the Yangtze River estuary

A strictly aerobic, Gram-negative, non-pigmented bacterial strain, designated LMEB 39(T), was isolated from a seawater sample collected from the Yangtze River estuary near the East China Sea and was examined physiologically, chemotaxonomically and phylogenetically. The novel isolate was motile by a single polar flagellum and positive for nitrate reduction and decomposition of casein, gelatin, Tween 20 and Tween 80, but negative for indole production. Chemotaxonomic analysis revealed ubiquinone-8 as the predominant respiratory quinone and phosphatidylethanolamine and phosphatidylglycerol as major polar lipids. The major fatty acids were C(16 : 1) ω 7c/iso-C(15 : 0) 2-OH, C(16 : 0), C(18 : 1) ω 7c, C(12 : 0) 3-OH, C(17 : 1)ω 8c and C(17 : 0). The genomic DNA G+C content was 42.3 mol%. Comparative 16S rRNA gene sequence analysis revealed that the isolate belongs to the genus Pseudoalteromonas. Strain LMEB 39(T) exhibited the closest phylogenetic affinity to Pseudoalteromonas byunsanensis JCM 12483(T) (97.4 % sequence similarity). The DNA-DNA reassociation values between strain LMEB 39(T) and P. byunsanensis JCM 12483(T) and Pseudoalteromonas undina DSM 6065(T) (97.2 % sequence similarity) were 31.7 and 30.3 %, respectively. On the basis of phenotypic and genotypic data, strain LMEB 39(T) represents a novel species of the genus Pseudoalteromonas, for which the name Pseudoalteromonas lipolytica sp. nov. is proposed; the type strain is LMEB 39(T) (=CGMCC 1.8499(T)=JCM 15903(T)).

Bacterial diversity and bioprospecting for cold-active lipases, amylases and proteases, from culturable bacteria of kongsfjorden and Ny-alesund, Svalbard, Arctic

Culturable bacterial diversity of seven marine sediment samples of Kongsfjorden and a sediment and a soil sample from Ny-Alesund, Svalbard, Arctic was studied. The bacterial abundance in the marine sediments of Kongsfjorden varied marginally (0.5 x 10(3)-1.3 x 10(4) cfu/g sediment) and the bacterial number in the two samples collected from the shore of Ny-Alesund also was very similar (0.6 x 10(4) and 3.4 x 10(4), respectively). From the nine samples a total of 103 bacterial isolates were obtained and these isolates could be grouped in to 47 phylotypes based on the 16S rRNA gene sequence belonging to 4 phyla namely Actinobacteria, Bacilli, Bacteroidetes and Proteobacteria. Representatives of the 47 phylotypes varied in their growth temperature range (4-37 degrees C), in their tolerance to NaCl (0.3-2 M NaCl) and growth pH range (2-11). Representatives of 26 phylotypes exhibited amylase and lipase activity either at 5 or 20 degrees C or at both the temperatures. A few of the representatives exhibited amylase and/or lipase activity only at 5 degrees C. None of the phylotypes exhibited protease activity. Most of the phylotypes (38) were pigmented. Fatty acid profile studies indicated that short chain fatty acids, unsaturated fatty acids, branched fatty acids, the cyclic and the cis fatty acids are predominant in the psychrophilic bacteria.