Cell Wall Murein Research Articles

Structural investigation of the capsular polysaccharide from a clinical isolate of Fusobacterium necrophorum subspecies necrophorum biotype a strain LA 81–617

A capsular polysaccharide (CPS) from Fusobacterium necrophorum subspecies necrophorum biotype A strain LA 81–617 was isolated from a saline cell wash and purified by gel and anion-exchange chromatography. The structure of the CPS was studied by one- and two-dimensional 1H and 13C NMR spectroscopy techniques in combination with electrospray ionization mass spectrometry (ESI-MS). The CPS was found to resemble the bacterial cell-wall murein polysaccharide backbone, consisting of N-acetylglucosamine and N-acetylmuramic acid (MurNAc) components, with the following structure:-[-4-β-MurNAc-4-β-GlcNAc-]n-with N-acetyl-1,6-anhydro-β-muramic acid at the reducing end. This is the first report on the structure of F. necrophorum capsular polysaccharide.

Catenisphaera adipataccumulans gen. nov., sp. nov., a member of the family Erysipelotrichaceae isolated from an anaerobic digester.

An obligately anaerobic bacterium, designated strain GK12(T), was isolated from an anaerobic digester in Fukagawa, Hokkaido Prefecture, Japan. The cells of strain GK12(T) were non-motile, non-spore-forming cocci that commonly occurred in chains. 16S rRNA gene sequence analysis revealed that strain GK12(T) was affiliated with the family Erysipelotrichaceae in the phylum Firmicutes and showed 91.8 % sequence similarity to the most closely related species, Faecalicoccus acidiformans. The strain grew at 30-50 °C (optimally at 40 °C) and at pH 5.5-8.5 (optimally at pH 7.5). The main end product of glucose fermentation was lactate. Yeast extract was required for growth. The strain contained C14 : 0, C14 : 0 1,1-dimethoxyalkane (DMA), C16 : 0 DMA and C18 : 0 DMA as the major cellular fatty acids (>10 % of the total). The polar lipid profile was composed of phosphatidylglycerol, phosphatidylinositol and an unidentified phospholipid. The whole-cell sugars were galactose, rhamnose and ribose. The cell-wall murein contained alanine, glutamic acid, lysine, serine and threonine, but not diaminopimelic acid. The G+C content of the genomic DNA was 47.7 mol%. Based on phenotypic, phylogenetic and chemotaxonomic properties, a novel genus and species, Catenisphaera adipataccumulans gen. nov., sp. nov., is proposed to accommodate strain GK12(T) ( = NBRC 108915(T) = DSM 25799(T)).

Canibacter oris gen. nov., sp. nov., isolated from an infected human wound

A facultatively anaerobic, Gram-reaction-positive, catalase- and oxidase-negative, rod-shaped bacterium isolated from an infected human wound caused by a dog bite was characterized by phenotypic and molecular genetic methods. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain IMMIB Q2029717T was a member of the order Micrococcales of the class Actinobacteria, displaying 91.6% to 96% sequence similarity with members of the family Microbacteriaceae. Phylogentic trees generated by different algorithms indicated that the strain forms an independent phylogenetic line of descent that consistently clustered proximal to the base of the genus Leucobacter. Chemical studies revealed the presence of a cell-wall murein based on L-lysine (type B1α), major menaquinone (MK-10) and a DNA G+C content of 56.9 mol%. The distinct phylogenetic position, ribotyping and matrix-assisted laser desorption/ionization time-of-flight MS profiles and the significant phenotypic differences clearly separate strain IMMIB Q2029717T from its nearest phylogenetic neighbour and support its classification as a representative of a novel genus and species, with the suggested name Canibacter oris gen. nov., sp. nov. The type strain is IMMIB Q2029717T (=DSM 27064T=CCUG 64069T).

N-acetylglucosamine-6-phosphate deacetylase (NagA) of Listeria monocytogenes EGD, an essential enzyme for the metabolism and recycling of amino sugars.

The main aim of our study was to determine the physiological function of NagA enzyme in the Listeria monocytogenes cell. The primary structure of the murein of L. monocytogenes is very similar to that of Escherichia coli, the main differences being amidation of diaminopimelic acid and partial de-N-acetylation of glucosamine residues. NagA is needed for the deacetylation of N-acetyl-glucosamine-6 phosphate to glucosamine-6 phosphate and acetate. Analysis of the L. monocytogenes genome reveals the presence of two proteins with NagA domain, Lmo0956 and Lmo2108, which are cytoplasmic putative proteins. We introduced independent mutations into the structural genes for the two proteins. In-depth characterization of one of these mutants, MN1, deficient in protein Lmo0956 revealed strikingly altered cell morphology, strongly reduced cell wall murein content and decreased sensitivity to cell wall hydrolase, mutanolysin and peptide antibiotic, colistin. The gene products of operon 150, consisting of three genes: lmo0956, lmo0957, and lmo0958, are necessary for the cytosolic steps of the amino-sugar-recycling pathway. The cytoplasmic de-N-acetylase Lmo0956 of L. monocytogenes is required for cell wall peptidoglycan and teichoic acid biosynthesis and is also essential for bacterial cell growth, cell division, and sensitivity to cell wall hydrolases and peptide antibiotics.Electronic supplementary materialThe online version of this article (doi:10.1007/s00203-011-0752-3) contains supplementary material, which is available to authorized users.

Auritidibacter ignavus gen. nov., sp. nov., of the family Micrococcaceae isolated from an ear swab of a man with otitis externa, transfer of the members of the family Yaniellaceae Li et al. 2008 to the family Micrococcaceae and emended description of the suborder Micrococcineae

A Gram-reaction-positive, aerobic, catalase-positive, non-spore-forming, rod-shaped bacterium designated IMMIB L-1656(T) was isolated from an ear swab of a man and characterized using a polyphasic approach. 16S rRNA gene sequence analysis indicated that strain IMMIB L-1656(T) is related to members of the family Micrococcaceae (<95.1 % sequence similarity). Anaylsis using different phylogenetic algorithms consistently grouped strain IMMIB L-1656(T) with members of the genus Yaniella. The organism posessed a cell-wall murein based on L-lysine (variation A4α, type L-Lys-Gly-L-Glu), MK-10 as the predominant menaquinone and long-chain cellular fatty acids of straight-chain and branched-chain saturated types (with iso-C(15 : 0) and anteiso-C(17 : 0) predominating). The polar lipids included diphosphatidylglycerol, phosphatidylglycerol and phosphatidylinositol in addition to unknown glycolipids. The DNA G+C content was 59.7 mol%. Based on its distinctive genotypic and phenotypic characteristics, strain IMMIB L-1656(T) represents a novel species in a novel genus, for which the name Auritidibacter ignavus gen. nov., sp. nov. is proposed. We also propose that members of the family Yaniellaceae be transferred to the family Micrococcaceae with amendments to the description of the suborder Micrococcineae. The type strain of Auritidibacter ignavus is IMMIB L-1656(T) (=DSM 45359(T) =CCUG 57943(T)).

Lacticigenium naphtae gen. nov., sp. nov., a halotolerant and motile lactic acid bacterium isolated from crude oil

A novel lactic acid bacterium, strain MIC1-18(T), was isolated from crude oil collected at an oil-water well in Akita, Japan. Cells of strain MIC1-18(T) were found to be facultatively anaerobic, mesophilic, neutrophilic, Gram-negative, non-sporulating, motile by means of peritrichous flagella and oval rods, 1.8-2.5 mum long. Optimum growth was observed at 30 degrees C, pH 7.0 and 3 % (w/v) NaCl. Strain MIC1-18(T) produced acid from l-arabinose, ribose, glucose, fructose, mannose, N-acetylglucosamine, amygdalin, arbutin, salicin, cellobiose, maltose, sucrose, trehalose, gentiobiose and 5-ketogluconate. l-Lactic acid was the major end product from glucose. The major cellular fatty acid was C(16 : 1)omega7c. The cell-wall murein type was A4alpha containing Lys-Glu. The G+C content of the genomic DNA was 37.8 mol%. Phylogenetic analysis based on the 16S rRNA gene revealed that strain MIC1-18(T) was accommodated as a member of the lactic acid bacteria of the low-G+C content Gram-positive bacteria; the closest neighbour of this organism was Atopococcus tabaci CCUG 48253(T), with only 90.0 % sequence similarity. On the basis of the phenotypic features and phylogenetic position, a novel genus and species, Lacticigenium naphtae gen. nov., sp. nov., are proposed for strain MIC1-18(T) (=NBRC 101988(T)=DSM 19658(T)).

Salinicoccus salitudinis sp. nov., a new moderately halophilic bacterium isolated from a saline soil sample

A novel pale-yellow-pigmented, moderately halophilic, facultatively alkaliphilic, non-motile, non-spore-forming, catalase- and oxidase-positive, obligately aerobic Gram-positive coccus, strain YIM-C678T was isolated from a saline soil sample collected from a hypersaline habitat in the Qaidam basin, northwest China. The organism grew at 4-37 degrees C and pH 6.0-11.0, with optimum growth at 25 degrees C and pH 8.0. Strain YIM-C678T grew optimally in the presence of 10-12% (w/v) NaCl and growth was observed in 1-25% (w/v) NaCl. The cell wall murein type was L: -Lys-Gly5. Major cellular fatty acids were anteiso-C15:0, iso-C15:0, iso-C16:0 and C16:0. Menaquinone 6 (MK-6) was the major respiratory quinone. The DNA G + C content was 46.5 mol%. Phylogenetic analysis based on 16S rRNA gene sequences indicated that the strain YIM-C678T belonged to the family Staphylococcaceae and was most closely related to the eight described species of the genus Salinicoccus with sequence similarities from 92.2 (S. luteus YIM 70202T) to 97.5% (S. kunmingensis YIM Y15T). The DNA-DNA relatedness between strain YIM-C678T and S. kunmingensis YIM Y15T was 35.4%. Chemotaxonomic data and 16S rRNA gene sequence analysis supported the affiliation of strain YIM-C678T with the genus Salinicoccus. The combination of phylogenetic analysis, phenotypic characteristics, chemotaxonomic differences and DNA-DNA hybridization data supported the view that the bacterium represents a novel species of the genus Salinicoccus, for which the name Salinicoccus salitudinis sp. nov. is proposed, with YIM-C678T (=DSM 17846 = CGMCC 1.6299) as the type strain.

Salinicoccus jeotgali sp. nov., isolated from jeotgal, a traditional Korean fermented seafood

A novel, moderately halophilic, Gram-positive coccus, designated strain S2R53-5(T), was isolated from jeotgal, a traditional Korean fermented seafood. The organism was strictly aerobic, non-motile, non-sporulating and catalase- and oxidase-positive. Strain S2R53-5(T) grew in the presence of 0.5-15 % (w/v) NaCl and at pH 6.5-11.0, with optimum growth at 5 % (w/v) NaCl and pH 7.0. The temperature range for growth was 20.0-30.0 degrees C, with an optimum temperature of 30 degrees C. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain S2R53-5(T) belongs to the family Staphylococcaceae and was most closely related to Salinicoccus roseus DSM 5351(T) (96.8 % gene sequence similarity), Salinicoccus hispanicus DSM 5352(T) (96.1 %), Salinicoccus alkaliphilus T8(T) (95.2 %) and Jeotgalicoccus halotolerans YKJ-101(T) (95.1 %). The genomic DNA G+C content was 47.0 mol%, which is in the range of 46-51 mol% that is characteristic for the genus Salinicoccus. Levels of DNA-DNA relatedness between strain S2R53-5(T) and S. roseus DSM 5351(T), S. hispanicus DSM 5352(T) and S. alkaliphilus KCTC 13928(T) were 32.2, 15.4 and 4.6 %, respectively. Chemotaxonomic data (major menaquinone, MK-6; major fatty acids, iso-C(15 : 0) and anteiso-C(15 : 0); cell-wall murein type, Lys and Gly) and 16S rRNA gene sequence analysis supported the affiliation of strain S2R53-5(T) with the genus Salinicoccus. The combined evidence from the low DNA-DNA relatedness, physiological, biochemical and other genotypic data indicate that strain S2R53-5(T) clearly represents a novel species of the genus Salinicoccus, for which the name Salinicoccus jeotgali sp. nov. is proposed. The type strain is S2R53-5(T) (=KCTC 13030(T)=LMG 23640(T)).

MurQ Etherase Is Required by Escherichia coli in Order To Metabolize Anhydro- N -Acetylmuramic Acid Obtained either from the Environment or from Its Own Cell Wall

MurQ is an N-acetylmuramic acid-phosphate (MurNAc-P) etherase that converts MurNAc-P to N-acetylglucosamine-phosphate and is essential for growth on MurNAc as the sole source of carbon (T. Jaegar, M. Arsic, and C. Mayer, J. Biol. Chem. 280:30100-30106, 2005). Here we show that MurQ is the only MurNAc-P etherase in Escherichia coli and that MurQ and AnmK kinase are required for utilization of anhydro-MurNAc derived either from cell wall murein or imported from the medium.

Catellicoccus marimammalium gen. nov., sp. nov., a novel Gram-positive, catalase-negative, coccus-shaped bacterium from porpoise and grey seal

Two strains of an unknown Gram-positive, catalase-negative, facultatively anaerobic, coccus-shaped bacterium, originating from a porpoise and a grey seal, were characterized using phenotypic, biochemical and molecular phylogenetic methods. Chemical studies revealed the presence of a cell-wall murein based on L-lysine (type L-lys-gly-D-Asp) and a DNA G+C content of 38 mol%. Comparative 16S rRNA gene sequencing showed that this unidentified coccus-shaped organism formed a hitherto unknown subline closely related to, albeit distinct from, a number of other catalase-negative genera which included Enterococcus, Melissococcus, Tetragenococcus and Vagococcus. Other known Gram-positive, catalase-negative taxa were more distantly related. Tree-branching considerations and sequence divergence values of >6% with recognized taxa were indicative of this novel bacterium representing a separate genus. Based on phenotypic and phylogenetic evidence, it is proposed that this unknown bacterium, recovered from a porpoise and a grey seal, be classified as a novel genus and species, Catellicoccus marimammalium gen. nov., sp. nov. The type strain is M35/04/3T (=CCUG 49459T=CIP 108575T).

Scission of the Lactyl Ether Bond of N-Acetylmuramic Acid by Escherichia coli “Etherase”

The ubiquitous bacterial cell wall sugar N-acetylmuramic acid (MurNAc) carries a unique D-lactyl ether substituent at the C3 position. Recently, we proposed an etherase capable of cleaving this lactyl ether to be part of the novel bacterial MurNAc dissimilation pathway (Dahl, U., Jaeger, T., Nguyen, B. T., Sattler, J. M., Mayer, C. (2004) J. Bacteriol. 186, 2385-2392). Here, we report the identification of the first known MurNAc etherase. The encoding gene murQ is located at 55 min on the Escherichia coli chromosome adjacent to murP, the MurNAc-specific phosphotransferase system. A murQ deletion mutant could not grow on MurNAc as the sole source of carbon and energy but could be complemented by expressing murQ from a plasmid. The mutant had no obvious phenotype when grown on different carbon sources but accumulated MurNAc 6-phosphate at millimolar concentrations from externally supplied MurNAc. Purified MurQ-His6 fusion protein and extracts of cells expressing murQ both catalyze the cleavage of MurNAc 6-phosphate, with GlcNAc 6-phosphate and D-lactate being the primary products. The 18O label from enriched water is incorporated into the sugar molecule, showing that the C3-O bond is cleaved and reformed by the enzyme. Moreover, an intermediate was detected and identified as an unsaturated sugar molecule. Based on this observation, we suggested a lyase-type mechanism (beta-elimination/hydration) for the cleavage of the lactyl ether bond of MurNAc 6-phosphate. Close homologs of murQ were found on the chromosome of several bacteria, and amino acid sequence similarity with the N-terminal domain of human glucokinase-regulatory protein (GckR or GKRP) was recognized.

Atopococcus tabaci gen. nov., sp. nov., a novel Gram-positive, catalase-negative, coccus-shaped bacterium isolated from tobacco

A novel Gram-positive, aerobic, catalase-negative, coccus-shaped organism originating from tobacco was characterized using phenotypic and molecular taxonomic methods. The organism contained a cell wall murein based on L-lysine (variation A4alpha, type L-lysine-L-glutamic acid), synthesized long-chain cellular fatty acids of the straight-chain saturated and monounsaturated types (with C(16:1)omega9, C(16:0) and C(18:1)omega9 predominating) and possessed a DNA G+C content of 46 mol%. Based on morphological, biochemical and chemical characteristics, the coccus-shaped organism did not conform to any presently recognized taxon. Comparative 16S rRNA gene sequencing studies confirmed the distinctiveness of the unknown coccus, with the bacterium displaying sequence divergence values of greater than 7% with other recognized Gram-positive taxa. Treeing analysis reinforced its distinctiveness, with the unidentified organism forming a relatively long subline branching at the periphery of an rRNA gene sequence cluster which encompasses the genera Alloiococcus, Allofustis, Alkalibacterium, Atopostipes, Dolosigranulum and Marinilactibacillus. Based on phenotypic and molecular phylogenetic evidence, it is proposed that the unknown organism from tobacco be classified as a new genus and species, Atopococcus tabaci gen. nov., sp. nov. The type strain of Atopococcus tabaci is CCUG 48253(T) (=CIP 108502(T)).

Recycling of the Anhydro- N -Acetylmuramic Acid Derived from Cell Wall Murein Involves a Two-Step Conversion to N -Acetylglucosamine-Phosphate

Escherichia coli breaks down over 60% of the murein of its side wall and reuses the component amino acids to synthesize about 25% of the cell wall for the next generation. The amino sugars of the murein are also efficiently recycled. Here we show that the 1,6-anhydro-N-acetylmuramic acid (anhMurNAc) is returned to the biosynthetic pathway by conversion to N-acetylglucosamine-phosphate (GlcNAc-P). The sugar is first phosphorylated by anhydro-N-acetylmuramic acid kinase (AnmK), yielding MurNAc-P, and this is followed by action of an etherase which cleaves the bond between D-lactic acid and the N-acetylglucosamine moiety of MurNAc-P, yielding GlcNAc-P. The kinase gene has been identified by a reverse genetics method. The enzyme was overexpressed, purified, and characterized. The cell extract of an anmK deletion mutant totally lacked activity on anhMurNAc. Surprisingly, in the anmK mutant, anhMurNAc did not accumulate in the cytoplasm but instead was found in the medium, indicating that there was rapid efflux of free anhMurNAc.

The N-acetyl-D-glucosamine kinase of Escherichia coli and its role in murein recycling.

N-acetyl-D-glucosamine (GlcNAc) is a major component of bacterial cell wall murein and the lipopolysaccharide of the outer membrane. During growth, over 60% of the murein of the side wall is degraded, and the major products, GlcNAc-anhydro-N-acetylmuramyl peptides, are efficiently imported into the cytoplasm and cleaved to release GlcNAc, anhydro-N-acetylmuramic acid, murein tripeptide (L-Ala-D-Glu-meso-diaminopimelic acid), and D-alanine. Like murein tripeptide, GlcNAc is readily recycled, and this process was thought to involve phosphorylation, since GlcNAc-6-phosphate (GlcNAc-6-P) is efficiently used to synthesize murein or lipopolysaccharide or can be metabolized by glycolysis. Since the gene for GlcNAc kinase had not been identified, in this work we purified GlcNAc kinase (NagK) from Escherichia coli cell extracts and identified the gene by determining the N-terminal sequence of the purified kinase. A nagK deletion mutant lacked phosphorylated GlcNAc in its cytoplasm, and the cell extract of the mutant did not phosphorylate GlcNAc, indicating that NagK is the only GlcNAc kinase expressed in E. coli. Unexpectedly, GlcNAc did not accumulate in a nagK nagEBACD mutant, though both GlcNAc and GlcNAc-6-P accumulate in the nagEBACD mutant, suggesting the existence of an alternative pathway (presumably repressed by GlcNAc-6-P) that reutilizes GlcNAc without the involvement of NagK.

Arsenicicoccus bolidensis gen. nov., sp. nov., a novel actinomycete isolated from contaminated lake sediment.

An unknown Gram-positive, catalase-positive, facultatively anaerobic, non-spore-forming, coccus-shaped bacterium originating from sediment was characterized using phenotypic, molecular chemical and molecular phylogenetic methods. Chemical studies revealed the presence of a cell-wall murein based on LL-diaminopimelic acid (type LL-Dpm-glycine(1)), a complex mixture of saturated, monounsaturated and iso- and anteiso-methyl-branched, non-hydroxylated, long-chain cellular fatty acids and tetrahydrogenated menaquinones with eight isoprene units [MK-8(H(4))] as the major respiratory lipoquinone. This combination of characteristics somewhat resembled members of the suborder Micrococcineae, but did not correspond to any currently described species. Comparative 16S rRNA gene sequencing confirmed that the unidentified coccus-shaped organism is a member of the Actinobacteria and represents a hitherto-unknown subline related to, albeit different from, a number of taxa including Intrasporangium, Janibacter, Terrabacter, Terracoccus and Ornithinicoccus. Based on phenotypic and phylogenetic considerations, it is proposed that the unknown bacterium originating from lake sediment be classified as a new genus and species, Arsenicicoccus bolidensis gen. nov., sp. nov. (type strain CCUG 47306(T)=DSM 15745(T)).

Luteococcus sanguinis sp. nov., isolated from human blood.

An unusual catalase-positive, Gram-positive, coccus-shaped bacterium that originated from a human blood specimen was subjected to a polyphasic taxonomic study. Cell-wall murein and lipid composition analyses indicated that the unknown isolate was a member of the genus Luteococcus. The results of comparative 16S rRNA gene sequence analysis were consistent with chemotaxonomic findings and showed that the unidentified bacterium represents a hitherto unknown sublineage within the genus Luteococcus that is closely related to, but distinct from, Luteococcus japonicus. On the basis of both phenotypic and phylogenetic evidence, it is proposed that the unknown bacterium from human blood should be classified as Luteococcus sanguinis sp. nov., with the type strain CCUG 33897(T) (=CIP 107216(T)).

Facilitation of horizontal transfer of antimicrobial resistance by transformation of antibiotic-induced cell-wall-deficient bacteria

It is universally accepted that the use of antibiotics will lead to antimicrobial resistance. Traditionally, the explanation to this phenomenon was random mutation and horizontal gene transfer and amplification by selective pressure. Subsequently, a second mechanism of antibiotic-induced antimicrobial resistance acquisition was proposed, when Davies et al. discovered that genes encoding antimicrobial resistance are present in bacteria that produce antibiotics, and during the process of antibiotic purification from these antibiotic-producing organisms, remnants of the organisms’ DNA that contain antibiotic resistance genes are also co-extracted, and can be recovered in antibiotic preparations. In addition to selective pressure and antimicrobial resistance genes in antibiotic preparations, we hypothesize the third mechanism by which administration of antibiotics leads to antimicrobial resistance. β-Lactams and glycopeptides damage bacteria by inhibiting cell wall murein synthesis. During the process, cell-wall-deficient forms are generated before the bacteria die. These cell-wall-deficient forms have an increased ability to uptake DNA by transformation. It has been demonstrated that plasmids encoding antimicrobial resistance of Staphylococcus aureus can be transformed to Bacillus subtilis after the B. subtilis was treated with penicillin or lysostaphin, a chemical that damage the cell walls of some Gram-positive bacteria; and that short treatment of Escherichia coli with antibiotics disturbing bacterial cell wall synthesis rendered the cells capable of absorbing foreign DNA. Since bacteria occupying the same ecological niche, such as the lower gastrointestinal tract, is common, bacteria are often incubated with foreign DNA encoding resistance coming from the administration of antibiotics or other bacteria that undergone lysis unrelated to antibiotic-induced killing. As few as a single antibiotic resistant gene is taken up by the cell-wall-deficient form, it will develop into a resistant clone, despite most of the other bacteria are killed by the antibiotic. If the hypothesis is correct, one should reduce the use of antibiotics that perturb bacterial cell wall synthesis, such as β-lactams, which is the largest group being manufactured, in both humans and animals, in order to reduce the acquisition of antibiotic resistance through this mechanism. In contrast to the old theory that antibiotics only provide selective pressures for the development of antimicrobial resistance, antibiotics by themselves are able to generate the whole chain of events towards the development of antimicrobial resistance. Antibiotics provide a source of antimicrobial resistance genes, facilitate the horizontal transfer of antimicrobial resistance genes through facilitating transformation, and provide selective pressures for amplification of the antimicrobial resistance genes. That is perhaps an important reason why antimicrobial resistance is so difficult to control. Further experiments should be performed to delineate which particular type of β-lactam antibiotics are associated with increase in transformation efficiencies more than the others, so that we can select those less resistance generating β-lactam for routine usage.

Allofustis seminis gen. nov., sp. nov., a novel Gram-positive, catalase-negative, rod-shaped bacterium from pig semen.

An unknown Gram-positive, catalase-negative, facultatively anaerobic, non-spore-forming, rod-shaped bacterium originating from semen of a pig was characterized using phenotypic, molecular chemical and molecular phylogenetic methods. Chemical studies revealed the presence of a directly cross-linked cell wall murein based on L-lysine and a DNA G + C content of 39 mol%. Comparative 16S rRNA gene sequencing showed that the unidentified rod-shaped organism formed a hitherto unknown subline related, albeit loosely, to Alkalibacterium olivapovliticus, Alloiococcus otitis, Dolosigranulum pigrum and related organisms, in the low-G + C-content Gram-positive bacteria. However, sequence divergence values of > 11% from these recognized taxa clearly indicated that the novel bacterium represents a separate genus. Based on phenotypic and phylogenetic considerations, it is proposed that the unknown bacterium from pig semen be classified as a new genus and species, Allofustis seminis gen. nov., sp. nov. The type strain is strain 01-570-1(T) (= CCUG 45438(T) = CIP 107425(T)).

Isobaculum melis gen. nov., sp. nov., a Carnobacterium-like organism isolated from the intestine of a badger.

Phenotypic and phylogenetic studies were performed on a hitherto undescribed facultatively anaerobic, catalase-negative, gram-positive rod-shaped organism, strain M577-94T, isolated from the small intestine of a dead badger. It resembled carnobacteria in terms of its long-chain cellular fatty acid composition, but differed markedly from the latter in possessing a cell-wall murein based on L-lysine (type L-Lys-L-Thr-Gly). Comparative 16S rRNA gene sequencing showed that the unknown bacterium represents a new line closely related to, albeit distinct from, the genera Carnobacterium and Desemzia. On the basis of phylogenetic and phenotypic evidence, it is proposed that strain M577-94T be classified as Isobaculum melis gen. nov., sp. nov. The type strain of Isobaculum melis is CCUG 37660T (= DSM 13760T).

Identification of a dedicated recycling pathway for anhydro-N-acetylmuramic acid and N-acetylglucosamine derived from Escherichia coli cell wall murein.

Turnover and recycling of the cell wall murein represent a major metabolic pathway of Escherichia coli. It is known that E. coli efficiently reuses, i.e., recycles, its murein tripeptide, L-alanyl-gamma-D-glutamyl-meso-diaminopimelate, to form new murein. However, the question of whether the cells also recycle the amino sugar moieties of cell wall murein has remained unanswered. It is demonstrated here that E. coli recycles the N-acetylglucosamine present in cell wall murein degradation products for de novo murein and lipopolysaccharide synthesis. Furthermore, E. coli also recycles the anhydro-N-acetylmuramic acid moiety by first converting it into N-acetylglucosamine. Based on the results obtained by studying mutants unable to recycle amino sugars, the pathway for recycling is revealed.