Reclassification of 'Pseudomonas fluorescens subsp. cellulosa' NCIMB 10462 (Ueda et al. 1952) as Cellvibrio japonicus sp. nov. and revival of Cellvibrio vulgaris sp. nov., nom. rev. and Cellvibrio fulvus sp. nov., nom. rev

Galactomannan utilization by Cellvibrio japonicus relies on a single essential α-galactosidase encoded by the aga27A gene

Plant mannans are a component of lignocellulose that can have diverse compositions in terms of its backbone and side-chain substitutions. Consequently, the degradation of mannan substrates requires a cadre of enzymes for complete reduction to substituent monosaccharides that can include mannose, galactose, and/or glucose. One bacterium that possesses this suite of enzymes is the Gram-negative saprophyte Cellvibrio japonicus, which has 10 predicted mannanases from the Glycoside Hydrolase (GH) families 5, 26, and 27. Here we describe a systems biology approach to identify and characterize the essential mannan-degrading components in this bacterium. The transcriptomic analysis uncovered significant changes in gene expression for most mannanases, as well as many genes that encode carbohydrate active enzymes (CAZymes) when mannan was actively being degraded. A comprehensive mutational analysis characterized 54 CAZyme-encoding genes in the context of mannan utilization. Growth analysis of the mutant strains found that the man26C, aga27A, and man5D genes, which encode a mannobiohydrolase, α-galactosidase, and mannosidase, respectively, were important for the deconstruction of galactomannan, with Aga27A being essential. Our updated model of mannan degradation in C. japonicus proposes that the removal of galactose sidechains from substituted mannans constitutes a crucial step for the complete degradation of this hemicellulose.

Cellvibrio polysaccharolyticus sp. nov., a cellulolytic bacterium isolated from agricultural soil

A novel Gram-reaction-negative bacterial strain, designated Ka43^T, was isolated from agricultural soil and characterised using a polyphasic approach to determine its taxonomic position. On the basis of 16S rRNA gene sequence analysis, the strain shows highest similarity (97.1 %) to Cellvibrio diazotrophicus E50^T. Cells of strain Ka43^T are aerobic, motile, short rods. The major fatty acids are summed feature 3 (C_16 : 1 ω7c and/or iso-C_15 : 0 2-OH), C_18 : 1  ω7c and C_16 : 0. The only isoprenoid quinone is Q-8. The polar lipid profile includes phosphatidylethanolamine, phosphatidylglycerol, four phospholipids, two lipids and an aminolipid. The assembled genome of strain Ka43^T has a total length of 4.2 Mb and the DNA G+C content is 51.6 mol%. Based on phenotypic data, including chemotaxonomic characteristics and analysis of the 16S rRNA gene sequences, it was concluded that strain Ka43^T represents a novel species in the genus Cellvibrio, for which the name Cellvibrio polysaccharolyticus sp. nov. is proposed. The type strain of the species is strain Ka43^T (=LMG 31577^T=NCAIM B.02637^T).

Genomic adaptation of Pseudomonas strains to acidity and antibiotics in hydrothermal vents at Kolumbo submarine volcano, Greece

Although the rise of antibiotic and multidrug resistant bacteria is one of the biggest current threats to human health, our understanding of the mechanisms involved in antibiotic resistance selection remains scarce. We performed whole genome sequencing of 21 Pseudomonas strains, previously isolated from an active submarine volcano of Greece, the Kolumbo volcano. Our goal was to identify the genetic basis of the enhanced co-tolerance to antibiotics and acidity of these Pseudomonas strains. Pangenome analysis identified 10,908 Gene Clusters (GCs). It revealed that the numbers of phage-related GCs and sigma factors, which both provide the mechanisms of adaptation to environmental stressors, were much higher in the high tolerant Pseudomonas strains compared to the rest ones. All identified GCs of these strains were associated with antimicrobial and multidrug resistance. The present study provides strong evidence that the CO2-rich seawater of the volcano associated with low pH might be a reservoir of microorganisms carrying multidrug efflux-mediated systems and pumps. We, therefore, suggest further studies of other extreme environments (or ecosystems) and their associated physicochemical parameters (or factors) in the rise of antibiotic resistance.

Trehalose Degradation by Cellvibrio japonicus Exhibits No Functional Redundancy and Is Solely Dependent on the Tre37A Enzyme

The α-diglucoside trehalose has historically been known as a component of the bacterial stress response, though it more recently has been studied for its relevance in human gut health and biotechnology development. The utilization of trehalose as a nutrient source by bacteria relies on carbohydrate-active enzymes, specifically those of the glycoside hydrolase family 37 (GH37), to degrade the disaccharide into substituent glucose moieties for entry into metabolism. Environmental bacteria using oligosaccharides for nutrients often possess multiple carbohydrate-active enzymes predicted to have the same biochemical activity and therefore are thought to be functionally redundant. In this study, we characterized trehalose degradation by the biotechnologically important saprophytic bacterium Cellvibrio japonicus This bacterium possesses two predicted α-α-trehalase genes, tre37A and tre37B, and our investigation using mutational analysis found that only the former is essential for trehalose utilization by C. japonicus Heterologous expression experiments found that only the expression of the C. japonicus tre37A gene in an Escherichia coli treA mutant strain allowed for full utilization of trehalose. Biochemical characterization of C. japonicus GH37 activity determined that the tre37A gene product is solely responsible for cleaving trehalose and is an acidic α-α-trehalase. Bioinformatic and mutational analyses indicate that Tre37A directly cleaves trehalose to glucose in the periplasm, as C. japonicus does not possess a phosphotransferase system. This study facilitates the development of a comprehensive metabolic model for α-linked disaccharides in C. japonicus and more broadly expands our understanding of the strategies that saprophytic bacteria employ to capture diverse carbohydrates from the environment.IMPORTANCE The metabolism of trehalose is becoming increasingly important due to the inclusion of this α-diglucoside in a number of foods and its prevalence in the environment. Bacteria able to utilize trehalose in the human gut possess a competitive advantage, as do saprophytic microbes in terrestrial environments. While the biochemical mechanism of trehalose degradation is well understood, what is less clear is how bacteria acquire this metabolite from the environment. The significance of this report is that by using the model saprophyte Cellvibrio japonicus, we were able to functionally characterize the two predicted trehalase enzymes that the bacterium possesses and determined that the two enzymes are not equivalent and are not functionally redundant. The results and approaches used to understand the complex physiology of α-diglucoside metabolism from this study can be applied broadly to other polysaccharide-degrading bacteria.

Complete Genome Sequences of Cellvibrio japonicus Strains with Improved Growth When Using α-Diglucosides

Cellvibrio japonicus is a saprophytic bacterium that has been studied for its substantial carbohydrate degradation capability. We announce the genome sequences of three strains with improved growth characteristics when utilizing α-diglucosides. These data provide additional insight into the metabolic flexibility of a biotechnologically relevant bacterium.

Cellvibrio japonicus is a saprophytic bacterium that has been studied for its substantial carbohydrate degradation capability. We announce the genome sequences of three strains with improved growth characteristics when utilizing α-diglucosides. These data provide additional insight into the metabolic flexibility of a biotechnologically relevant bacterium.

Ecological Functions of Agricultural Soil Bacteria and Microeukaryotes in Chitin Degradation: A Case Study

Chitin provides a valuable carbon and nitrogen source for soil microorganisms and is a major component of particulate organic matter in agricultural soils. To date, there is no information on interaction and interdependence in chitin-degrading soil microbiomes. Since microbial chitin degradation occurs under both oxic and anoxic conditions and both conditions occur simultaneously in soil, the comparison of the active microbiome members under both conditions can reveal key players for the overall degradation in aerated soil. A time-resolved 16S rRNA stable isotope probing experiment was conducted with soil material from the top soil layer of a wheat-covered field. [¹³C_U]-chitin was largely mineralized within 20 days under oxic conditions. Cellvibrio, Massilia, and several Bacteroidetes families were identified as initially active chitin degraders. Subsequently, Planctomycetes and Verrucomicrobia were labeled by assimilation of ¹³C carbon either from [¹³C_U]-chitin or from ¹³C-enriched components of primary chitin degraders. Bacterial predators (e.g., Bdellovibrio and Bacteriovorax) were labeled, too, and non-labeled microeukaryotic predators (Alveolata) increased their relative abundance toward the end of the experiment (70 days), indicating that chitin degraders were subject to predation. Trophic interactions differed substantially under anoxic and oxic conditions. Various fermentation types occurred along with iron respiration. While Acidobacteria and Chloroflexi were the first taxa to be labeled, although at a low ¹³C level, Firmicutes and uncultured Bacteroidetes were predominantly labeled at a much higher ¹³C level during the later stages, suggesting that the latter two bacterial taxa were mainly responsible for the degradation of chitin and also provided substrates for iron reducers. Eventually, our study revealed that (1) hitherto unrecognized Bacteria were involved in a chitin-degrading microbial food web of an agricultural soil, (2) trophic interactions were substantially shaped by the oxygen availability, and (3) detectable predation was restricted to oxic conditions. The gained insights into trophic interactions foster our understanding of microbial chitin degradation, which is in turn crucial for an understanding of soil carbon dynamics.

Genome dynamics and evolution in yeasts: A long-term yeast-bacteria competition experiment

There is an enormous genetic diversity evident in modern yeasts, but our understanding of the ecological basis of such diversifications in nature remains at best fragmented so far. Here we report a long-term experiment mimicking a primordial competitive environment, in which yeast and bacteria co-exist and compete against each other. Eighteen yeasts covering a wide phylogenetic background spanning approximately 250 million years of evolutionary history were used to establish independent evolution lines for at most 130 passages. Our collection of hundreds of modified strains generated through such a rare two-species cross-kingdom competition experiment re-created the appearance of large-scale genomic rearrangements and altered phenotypes important in the diversification history of yeasts. At the same time, the methodology employed in this evolutionary study would also be a non-gene-technological method of reprogramming yeast genomes and then selecting yeast strains with desired traits. Cross-kingdom competition may therefore be a method of significant value to generate industrially useful yeast strains with new metabolic traits.

Agarilytica rhodophyticola gen. nov., sp. nov., isolated from Gracilaria blodgettii

A novel Gram-stain-negative, rod-shaped, non-spore-forming, aerobic, agarolytic bacterium, designated 017^T, was isolated from Gracilaria blodgettii collected at the coast of Lingshui county, Hainan province, China. Optimal growth occurred at 28-33 °C (range 15-40 °C), with 3 % (w/v) NaCl (range 2-4 %) and at pH 8.0 (range pH 6.5-8.5). Cells of strain 017^T were motile and formed yellow colonies on marine agar 2216. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain 017^T shared the highest similarity with Teredinibacter turnerae T7902^T (94.4 %). The predominant polar lipids of the novel isolate consisted of phosphatidylglycerol, phosphatidylethanolamine, aminophospholipid and some other unknown lipids. Major cellular fatty acids (>10 %) were C16 : 0, C18 : 1ω7c and summed feature 3 (C16 : 1ω7c/iso-C15 : 0 2-OH), and the sole respiratory lipoquinone was Q-8. The DNA G+C content of strain 017^T was 40.2 mol%. Comparative analysis of 16S rRNA gene sequences and phenotypic characterization indicated that strain 017^T represents a novel species in a new genus of the family Cellvibrionaceae, order Cellvibrionales, for which the name Agarilytica rhodophyticola gen. nov., sp. nov. is proposed. The type strain of Agarilytica rhodophyticola is 017^T (=KCTC 42584^T=MCCC 1H00123^T).

Comparative Phenotype and Genome Analysis of Cellvibrio sp. PR1, a Xylanolytic and Agarolytic Bacterium from the Pearl River

Cellvibrio sp. PR1 is a xylanolytic and agarolytic bacterium isolated from the Pearl River. Strain PR1 is closely related to Cellvibrio fibrivorans and C. ostraviensis (identity > 98%). The xylanase and agarase contents of strain PR1 reach up to 15.4 and 25.9 U/mL, respectively. The major cellular fatty acids consisted of C16:0 (36.7%), C18:0 (8.8%), C20:0 (6.8%), C15:0 iso 2-OH or/and C16:1ω7c (17.4%), and C18:1ω7c or/and C18:1ω6c (6.7%). A total of 251 CAZyme modules (63 CBMs, 20 CEs, 128 GHs, 38 GTs, and 2 PLs) were identified from 3,730 predicted proteins. Genomic analysis suggested that strain PR1 has a complete xylan-hydrolyzing (5 β-xylanases, 16 β-xylosidases, 17 α-arabinofuranosidases, 9 acetyl xylan esterases, 4 α-glucuronidases, and 2 ferulic acid esterases) and agar-hydrolyzing enzyme system (2 β-agarases and 2 α-neoagarooligosaccharide hydrolases). In addition, the main metabolic pathways of xylose, arabinose, and galactose are established in the genome-wide analysis. This study shows that strain PR1 contains a large number of glycoside hydrolases.

Polysaccharide degradation systems of the saprophytic bacterium Cellvibrio japonicus

Study of recalcitrant polysaccharide degradation by bacterial systems is critical for understanding biological processes such as global carbon cycling, nutritional contributions of the human gut microbiome, and the production of renewable fuels and chemicals. One bacterium that has a robust ability to degrade polysaccharides is the Gram-negative saprophyte Cellvibrio japonicus. A bacterium with a circuitous history, C. japonicus underwent several taxonomy changes from an initially described Pseudomonas sp. Most of the enzymes described in the pre-genomics era have also been renamed. This review aims to consolidate the biochemical, structural, and genetic data published on C. japonicus and its remarkable ability to degrade cellulose, xylan, and pectin substrates. Initially, C. japonicus carbohydrate-active enzymes were studied biochemically and structurally for their novel polysaccharide binding and degradation characteristics, while more recent systems biology approaches have begun to unravel the complex regulation required for lignocellulose degradation in an environmental context. Also included is a discussion for the future of C. japonicus as a model system, with emphasis on current areas unexplored in terms of polysaccharide degradation and emerging directions for C. japonicus in both environmental and biotechnological applications.

Extremophiles in an Antarctic Marine Ecosystem

Recent attempts to explore marine microbial diversity and the global marine microbiome have indicated a large proportion of previously unknown diversity. However, sequencing alone does not tell the whole story, as it relies heavily upon information that is already contained within sequence databases. In addition, microorganisms have been shown to present small-to-large scale biogeographical patterns worldwide, potentially making regional combinations of selection pressures unique. Here, we focus on the extremophile community in the boundary region located between the Polar Front and the Southern Antarctic Circumpolar Current in the Southern Ocean, to explore the potential of metagenomic approaches as a tool for bioprospecting in the search for novel functional activity based on targeted sampling efforts. We assessed the microbial composition and diversity from a region north of the current limit for winter sea ice, north of the Southern Antarctic Circumpolar Front (SACCF) but south of the Polar Front. Although, most of the more frequently encountered sequences  were derived from common marine microorganisms, within these dominant groups, we found a proportion of genes related to secondary metabolism of potential interest in bioprospecting. Extremophiles were rare by comparison but belonged to a range of genera. Hence, they represented interesting targets from which to identify rare or novel functions. Ultimately, future shifts in environmental conditions favoring more cosmopolitan groups could have an unpredictable effect on microbial diversity and function in the Southern Ocean, perhaps excluding the rarer extremophiles.

Cellvibrio diazotrophicus sp. nov., a nitrogen-fixing bacteria isolated from the rhizosphere of salt meadow plants and emended description of the genus Cellvibrio

Two Gram-reaction-negative, aerobic, nitrogen-fixing, rod-shaped bacteria, designated strains E20 and E50(T), were isolated from the rhizosphere of salt meadow plants Plantago winteri and Hordeum secalinum, respectively, near Münzenberg, Germany. Based on the 16S rRNA gene sequence analysis both strains E20 and E50(T) are affiliated with the genus Cellvibrio, sharing the highest similarity with Cellvibrio gandavensis LMG 18551(T) (96.4%) and (97.1%), respectively. Strains E20 and E50(T) were oxidase and catalase-positive, grew at a temperature range between 16 and 37 °C and in the presence of 0-5% NaCl (w/v). The DNA G+C contents were 52.1 mol% (E20) and 51.6 mol% (E50(T)). Major fatty acids of strains E20 and E50(T) were summed feature 3 (C16 : 1ω7c and/or iso-C(15 : 0) 2-OH), C(16 : 0), C(18 : 1)ω7c, C(12 : 0), C(18 : 0) and C(12 : 0) 3-OH. The DNA-DNA relatedness of the strains to Cellvibrio gandavensis LMG 18551(T) was 39% for strain E20 and 58% for strain E50(T). The nitrogen fixation capability of strains E20 and E50(T) was confirmed by the acetylene reduction assay. On the basis of our polyphasic taxonomic study, strains E20 and E50(T) represent a novel species of the genus Cellvibrio, for which the name Cellvibrio diazotrophicus is proposed. The type strain of Cellvibrio diazotrophicus is E50(T) ( = LMG 27267(T) = KACC 17069(T)). An emended description of the genus Cellvibrio is proposed based on the capability of fixing nitrogen and growth in presence of up to 5% NaCl (w/v).

Structural enzymology of Cellvibrio japonicus Agd31B protein reveals α-transglucosylase activity in glycoside hydrolase family 31

The metabolism of the storage polysaccharides glycogen and starch is of vital importance to organisms from all domains of life. In bacteria, utilization of these α-glucans requires the concerted action of a variety of enzymes, including glycoside hydrolases, glycoside phosphorylases, and transglycosylases. In particular, transglycosylases from glycoside hydrolase family 13 (GH13) and GH77 play well established roles in α-glucan side chain (de)branching, regulation of oligo- and polysaccharide chain length, and formation of cyclic dextrans. Here, we present the biochemical and tertiary structural characterization of a new type of bacterial 1,4-α-glucan 4-α-glucosyltransferase from GH31. Distinct from 1,4-α-glucan 6-α-glucosyltransferases (EC 2.4.1.24) and 4-α-glucanotransferases (EC 2.4.1.25), this enzyme strictly transferred one glucosyl residue from α(1→4)-glucans in disproportionation reactions. Substrate hydrolysis was undetectable for a series of malto-oligosaccharides except maltose for which transglycosylation nonetheless dominated across a range of substrate concentrations. Crystallographic analysis of the enzyme in free, acarbose-complexed, and trapped 5-fluoro-β-glucosyl-enzyme intermediate forms revealed extended substrate interactions across one negative and up to three positive subsites, thus providing structural rationalization for the unique, single monosaccharide transferase activity of the enzyme.

Structural and enzymatic characterization of a glycoside hydrolase family 31 α-xylosidase from Cellvibrio japonicus involved in xyloglucan saccharification

The desire for improved methods of biomass conversion into fuels and feedstocks has re-awakened interest in the enzymology of plant cell wall degradation. The complex polysaccharide xyloglucan is abundant in plant matter, where it may account for up to 20% of the total primary cell wall carbohydrates. Despite this, few studies have focused on xyloglucan saccharification, which requires a consortium of enzymes including endo-xyloglucanases, α-xylosidases, β-galactosidases and α-L-fucosidases, among others. In the present paper, we show the characterization of Xyl31A, a key α-xylosidase in xyloglucan utilization by the model Gram-negative soil saprophyte Cellvibrio japonicus. CjXyl31A exhibits high regiospecificity for the hydrolysis of XGOs (xylogluco-oligosaccharides), with a particular preference for longer substrates. Crystallographic structures of both the apo enzyme and the trapped covalent 5-fluoro-β-xylosyl-enzyme intermediate, together with docking studies with the XXXG heptasaccharide, revealed, for the first time in GH31 (glycoside hydrolase family 31), the importance of a PA14 domain insert in the recognition of longer oligosaccharides by extension of the active-site pocket. The observation that CjXyl31A was localized to the outer membrane provided support for a biological model of xyloglucan utilization by C. japonicus, in which XGOs generated by the action of a secreted endo-xyloglucanase are ultimately degraded in close proximity to the cell surface. Moreover, the present study diversifies the toolbox of glycosidases for the specific modification and saccharification of cell wall polymers for biotechnological applications.

Zhongshania antarctica gen. nov., sp. nov. and Zhongshania guokunii sp. nov., gammaproteobacteria respectively isolated from coastal attached (fast) ice and surface seawater of the Antarctic

Two Gram-negative, motile, aerobic, catalase- and oxidase-positive, rod-shaped strains, designated ZS5-23(T) and ZS6-22(T), were respectively isolated from Antarctic coastal attached (fast) ice and surface seawater samples. Both strains could grow at 4-35 °C (optimum 30 °C) and in the absence of NaCl. Analyses of 16S rRNA gene sequences revealed that strains ZS5-23(T) and ZS6-22(T) were closely related to each other (99.0 % sequence similarity) and belonged to the class Gammaproteobacteria, with their closest relatives being Spongiibacter and Melitea species (93.1-94.3 % sequence similarity). The predominant cellular fatty acids in both strains were C₁₇:₁ω8c, C₁₇:₀ and summed feature 3 (C₁₆:₁ω7c and/or iso-C₁₅:₀ 2-OH). Genomic DNA G+C contents of strains ZS5-23(T) and ZS6-22(T) were 51.5 and 51.8 mol%, respectively. The DNA-DNA relatedness between strains ZS5-23(T) and ZS6-22(T) was 50.9 %. Strains ZS5-23(T) and ZS6-22(T) could be differentiated from each other and from Spongiibacter and Melitea species by differences in a number of phenotypic properties. Based on the data presented, strains ZS5-23(T) and ZS6-22(T) represent two novel species in a new genus in the class Gammaproteobacteria, for which the names Zhongshania antarctica gen. nov., sp. nov. (the type species) and Zhongshania guokunii sp. nov. are proposed. The type strain of Zhongshania antarctica is ZS5-23(T) ( = KACC 14066(T)  = CCTCC AB 209246(T)) and that of Zhongshania guokunii is ZS6-22(T) ( = KACC 14532(T)  = CCTCC AB 209247(T)).

Immobilization of Lactococcus lactis to cellulosic material by cellulose-binding domain of Cellvibrio japonicus

AIMS

Immobilization of whole cells can be used to accumulate cells in a bioreactor and thus increase the cell density and potentially productivity, also. Cellulose is an excellent matrix for immobilization purposes because it does not require chemical modifications and is commercially available in many different forms at low price. The aim of this study was to construct a Lactococcus lactis strain capable of immobilizing to a cellulosic matrix.

METHODS AND RESULTS

In this study, the Usp45 signal sequence fused with the cellulose-binding domain (CBD) (112 amino acids) of XylA enzyme from Cellvibrio japonicus was fused with PrtP or AcmA anchors derived from L. lactis. A successful surface display of L. lactis cells expressing these fusion proteins under the P45 promoter was achieved and detected by whole-cell ELISA. A rapid filter paper assay was developed to study the cellulose-binding capability of these recombinant strains. As a result, an efficient immobilization to filter paper was demonstrated for the L. lactis cells expressing the CBD-fusion protein. The highest immobilization (92%) was measured for the strain expressing the CBD in fusion with the 344 amino acid PrtP anchor.

CONCLUSIONS

The result from the binding tests indicated that a new phenotype for L. lactis with cellulose-binding capability was achieved with both PrtP (LPXTG type anchor) and AcmA (LysM type anchor) fusions with CBD.

SIGNIFICANCE AND IMPACT OF THE STUDY

We demonstrated that an efficient immobilization of recombinant L. lactis cells to cellulosic matrix is possible. This is a step forward in developing efficient immobilization systems for lactococcal strains for industrial-scale fermentations.

Requirement of the type II secretion system for utilization of cellulosic substrates by Cellvibrio japonicus

Cellulosic biofuels represent a powerful alternative to petroleum but are currently limited by the inefficiencies of the conversion process. While gram-positive and fungal organisms have been widely explored as sources of cellulases and hemicellulases for biomass degradation, gram-negative organisms have received less experimental attention. We investigated the ability of Cellvibrio japonicus, a recently sequenced gram-negative cellulolytic bacterium, to degrade bioenergy-related feedstocks. Using a newly developed biomass medium, we showed that C. japonicus is able to utilize corn stover and switchgrass as sole sources of carbon and energy for growth. We also developed tools for directed gene disruptions in C. japonicus and used this system to construct a mutant in the gspD gene, which is predicted to encode a component of the type II secretion system. The gspD::pJGG1 mutant displayed a greater-than-2-fold decrease in endoglucanase secretion compared to wild-type C. japonicus. In addition, the mutant strain showed a pronounced growth defect in medium with biomass as a carbon source, yielding 100-fold fewer viable cells than the wild type. To test the potential of C. japonicus to undergo metabolic engineering, we constructed a strain able to produce small amounts of ethanol from biomass. Collectively, these data suggest that C. japonicus is a useful platform for biomass conversion and biofuel production.

Porticoccus litoralis gen. nov., sp. nov., a gammaproteobacterium isolated from the Yellow Sea

A marine bacterium, designated IMCC2115T, was isolated from coastal seawater (Yellow Sea, Korea) using a high throughput cultivation method based on dilution-to-extinction, and taxonomically investigated. Cells of the strain formed tiny, beige to off-white colonies and were Gram-stain-negative, obligately aerobic, chemoheterotrophic, non-motile cocci. Based on 16S rRNA gene sequence comparisons, the strain was most closely related to the genera Marinimicrobium (92.0–92.4 %) and Microbulbifer (91.6–92.8 %), but phylogenetic trees showed that the strain formed a distinct phyletic line in the class Gammaproteobacteria adjacent to the OM60 and SAR92 clades. The DNA G+C content of the strain was 47.8 mol% and the predominant cellular fatty acids were anteiso-C15 : 0 (67.6 %), anteiso-C17 : 0 (14.4 %) and C16 : 0 (6.9 %). The 16S rRNA gene sequence analyses and phenotypic and chemotaxonomic tests allowed the differentiation of IMCC2115T from other related genera in the class Gammaproteobacteria. Therefore, strain IMCC2115T (=KCCM 42369T =NBRC 102686T) is proposed as the representative of a new genus and species, for which the name Porticoccus litoralis gen. nov., sp. nov. is proposed.

Insights into plant cell wall degradation from the genome sequence of the soil bacterium Cellvibrio japonicus

The plant cell wall, which consists of a highly complex array of interconnecting polysaccharides, is the most abundant source of organic carbon in the biosphere. Microorganisms that degrade the plant cell wall synthesize an extensive portfolio of hydrolytic enzymes that display highly complex molecular architectures. To unravel the intricate repertoire of plant cell wall-degrading enzymes synthesized by the saprophytic soil bacterium Cellvibrio japonicus, we sequenced and analyzed its genome, which predicts that the bacterium contains the complete repertoire of enzymes required to degrade plant cell wall and storage polysaccharides. Approximately one-third of these putative proteins (57) are predicted to contain carbohydrate binding modules derived from 13 of the 49 known families. Sequence analysis reveals approximately 130 predicted glycoside hydrolases that target the major structural and storage plant polysaccharides. In common with that of the colonic prokaryote Bacteroides thetaiotaomicron, the genome of C. japonicus is predicted to encode a large number of GH43 enzymes, suggesting that the extensive arabinose decorations appended to pectins and xylans may represent a major nutrient source, not just for intestinal bacteria but also for microorganisms that occupy terrestrial ecosystems. The results presented here predict that C. japonicus possesses an extensive range of glycoside hydrolases, lyases, and esterases. Most importantly, the genome of C. japonicus is remarkably similar to that of the gram-negative marine bacterium, Saccharophagus degradans 2-40(T). Approximately 50% of the predicted C. japonicus plant-degradative apparatus appears to be shared with S. degradans, consistent with the utilization of plant-derived complex carbohydrates as a major substrate by both organisms.

The Impact of Bioaugmentation on Metal Cyanide Degradation and Soil Bacteria Community Structure

Metal cyanides are significant contaminants of many soils found at the site of former industrial activity. In this study we isolated bacteria capable of degrading ferric ferrocyanide and K2Ni(CN)4. One of these bacteria a Rhodococcus spp. was subsequently used to bioaugment a minimal medium broth, spiked with K2Ni(CN)4, containing 1 g of either an uncontaminated topsoil or a former coke works site soil. Degradation of the K2Ni(CN)4 was observed in both soils, however, bioaugmentation did not significantly impact the rate or degree of K2Ni(CN)4 removal. Statistical analysis of denaturing gradient gel electrophoresis profiles showed that the topsoil bacterial community had a higher biodiversity, and its structure was not significantly affected by either K2Ni(CN)4 or bioaugmentation. In contrast, profiles from the coke works site indicated significant changes in the bacterial community in response to these additions. Moreover, in both soils although bioaugmentation did not affect rates of biodegradation the Rhodococcus spp. did become established in the communities in broths containing both top and coke works soil. We conclude that bacterial communities from contaminated soils with low biodiversity are much more readily perturbed through interventions such as contamination events or bioaugmentation treatments and discuss the implications of these findings for bioremediation studies.

Screening of novel cellulose-degrading bacterium and its application to denitrification of groundwater

To establish an environmentally friendly groundwater bioremediation process using a cellulose carrier combined with cellulose-utilizing, denitrifying microorganisms, a novel psychrophilic bacterium, designated CL-5, which can degrade a commercial-based cellulose carrier as the sole carbon source, was screened. Since the denitrification capability of CL-5 is low, complex microbial systems were constructed together with other denitrifying bacteria designated NR-1 and NR-2 that were also isolated from soil. The nitrate-reducing activities of mixed cultures were much higher than those of the pure cultures of CL-5, NR-1 and NR-2. The highest N(2)O and N(2) formation activities were observed in the mixed culture of CL-5+NR-2.