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PubMed1975

Effects of an abrupt change in ration from all roughage to high concentrate upon rumen microbial numbers in sheep.

When three sheep were abruptly changed from a ration of 100% orchardgrass hay to 60% cracked corn-40% orchardgrass hay, fed at equal dry-matter intakes, significant increases in concentration were observed in the rumen microbial population. Bacterial numbers (colony counts) per gram of rumen contents did not appear to have stabilized within 21 days after the ration change; however, protozoan numbers per milliliter plateaued after 5 days. The concentration of cellulose-digesting bacteria varied considerably between animals and decreased in all animals with the change. Changes were observed in total and molar percentages of volatile fatty acids, which were typical for the two types of rations. Although the concentration of protozoa increased after the ration change, only minor differences were observed in their percent generic distribution. A significant decrease in rumen volume was measured in two of the three sheep with the change in ration; however, fluid turnover rates were not significantly affected. Rates of rumen dry-matter turnover were slower with the concentrate ration, although rumen dry-matter digestion was increased. Calculation of total bacterial numbers based on total rumen volume completely negated the effect of ration change in one animal, whereas total numbers in the other two animals were still significantly different between rations and very similar between animals. Adjustment of total protozoa numbers did not alter the trends seen previously with concentration values.

Animal Feed↗
PubMed1966

Effect of 8-azaguanine on the transition from vegetative growth to presporulation in Bacillus cereus.

Stahly, D. P. (University of Illinois, Urbana), V. R. Srinivasan, and H. Orin Halvorson. Effect of 8-azaguanine on the transition from vegetative growth to presporulation in Bacillus cereus. J. Bacteriol. 91:1875-1882. 1966.-The guanine analogue, 8-azaguanine (azaG), was found to inhibit sporulation of Bacillus cereus strain T when added to proliferating cells, but not to inhibit when added after the transition to presporulation. When azaG was added to vegetative cells, the growth rate was reduced, but no immediate bactericidal effect was demonstrated. Azaguanine was shown to be incorporated solely into ribonucleic acid (RNA). All of the natural purine bases and nucleosides were found to prevent azaG inhibition by blocking incorporation of the analogue into the RNA. Addition of a subinhibitory level of C(14)-azaG to proliferating cells resulted in an increase in incorporation paralleling the increase in number of cells. At the time of transition from growth to presporulation, a rapid removal of the azaG label from the cells occurred in the absence of net RNA breakdown. If differentiation was inhibited by increasing the concentration of azaG, then no expulsion took place. Instead, at the end of growth, net incorporation ceased, and a steady-state condition was established in which incorporation equaled breakdown. No azaG degradative enzymes are present in presporulating cells. The possibility is discussed that an increase in the ratio of natural purines to azaG occurred at the time of transition, and that the natural purine derivatives then were reincorporated into RNA preferentially to azaG. The data are consistent with the hypothesis than an increased rate of RNA turnover occurs at the time of transition from vegetative growth to presporulation. Addition of phosphate buffer (pH 7.0, 0.1 m) to azaG-inhibited vegetative cells caused reversal of inhibition, the reversal being accompanied by expulsion of the azaG. At least a partial explanation of this effect is that phosphate causes a decrease in the azaG intracellular pool size.

Azaguanine↗
PubMed2004

Vancomycin-induced deletion of the methicillin resistance gene mecA in Staphylococcus aureus.

OBJECTIVE: To elucidate factors that contribute to the development of vancomycin resistance in methicillin-resistant Staphylococcus aureus (MRSA). METHODS: Forty-nine MRSA isolates were subjected to passage selection with vancomycin to isolate mutants with reduced susceptibility to vancomycin. One mutant was chosen for detailed molecular and biochemical characterization. RESULTS: Five vancomycin-resistant mutants (vancomycin MICs, 6-12 mg/L) were obtained in vitro from five MRSA parent isolates. Upon acquisition of vancomycin resistance, all mutants showed a concomitant decrease in oxacillin resistance. In one particular MRSA strain, selection for vancomycin resistance repeatedly produced deletions and rearrangements, including loss of the mecA gene. Pleiotropic phenotypical changes, such as yellow pigment formation, loss of haemolysis, thickened cell wall, increased resistance to lysostaphin and reduced cell wall turnover were observed in this mutant. CONCLUSION: Acquisition of vancomycin resistance in one MRSA strain triggered mecA deletion suggesting that this deletion, coupled to other rearrangements and/or mutations, may be responsible for the increased vancomycin resistance phenotype.

Anti-Bacterial Agents↗
PubMed1988

Microbial Decomposition in Aquatic Environments: Combined Process of Extracellular Enzyme Activity and Substrate Uptake.

The aim of this study was to define a model for the coupling between extracellular enzyme activity and substrate uptake by bacterial populations in natural waters. The balance between uptake of leucine and extracellular hydrolytic production of leucine from a peptide model substrate was investigated in a combined fluorescence-radiotracer experiment with [H]leucine as a marker for the leucine pool and l-leucine-4 methyl-7-coumarinylamide (Leu-MCA) as a marker for the pool of dissolved peptide substrates. Results show that at low concentrations of the model substrate the input and uptake processes of leucine are nearly balanced, whereas at high concentrations of the model substrate much more leucine is liberated than taken up. In addition, samples from one polluted and one less polluted station in the Kiel Fjord were investigated for their extracellular enzymatic and uptake properties in an annual cycle. It was found that turnover rates of leucine (T(r), percent per hour) and hydrolysis rates of Leu-MCA (H(r), percent per hour), as well as the quotient T(r)/H(r), reflect the impact of environmental conditions on decomposition processes at both sampling sites. The quotient T(r)/H(r) is interpreted as an indirect measurement of the pool size ratio (polymers/monomers), which may serve as an index of hydrolysis-uptake coupling in bacterial utilization of dissolved protein. Calculated on an annual average basis, turnover rates are ca. nine times higher than hydrolysis rates at the polluted station and ca. five times higher at the less polluted station. From the described model, this would mean that the relative fraction of polymers within the total dissolved organic carbon pool (with regard to the substrate combination dissolved protein-leucine) is about twice that at the polluted than at the less polluted station.

Journal Article↗
PubMed1982

Dynamics of protozoa in the rumen of sheep.

Protozoa were labelled by incubating 100 ml rumen fluid with [14C]choline for 1 h. The protozoa were concentrated by centrifugation and then washed with rumen fluid. This reduced residual 14C in the fluid medium to insignificant amounts while still retaining the viability of the labelled protozoa. Washing procedures using formal saline (40 g formaldehyde/1 saline (9 g sodium chloride/1)) and saline were developed to isolate protozoa for estimation of specific radioactivity. 2. The protozoal pool in freshly-collected rumen fluid incubated in vitro retained 90% of the radioactivity for up to 6 h following addition of 14C-labelled protozoa produced as indicated previously. The specific radioactivity of protozoa did not change during the incubation period. 3. Protozoa labelled with [14C]choline and then stored until they died rapidly lost 14C to methane when they were incubated in rumen fluid or were injected into the rumen. Some [14C]choline was salvaged under these conditions by the live protozoa present as they apparently incorporated up to 13% of the label from the dead protozoa. However, protozoal debris from the injected solution could also have been present in the isolated protozoa. 4. The in vitro results suggested that the protozoal preparations were viable, and that the incorporated choline did not have a turnover in excess of the turnover of nitrogen (i.e. specific radioactivity remained constant with time in vitro) suggesting that the dilution of specific radioactivity of protozoa following mixing of a 14C-labelled dose of protozoa represented the rate of irreversible loss and also replacement of protozoa in the rumen. 5. 14C-labelled protozoa had a half-life in the rumen which was greater than that of rumen fluid and in six animals the protozoal replacement rate was 1-4.1 mg N/min. 6. Losses of 14C from labelled protozoa in the rumen in methane or via abomasal digesta were 65 and 35% respectively. 7. The results suggest that protozoal growth may be as high as 32% of the total microbial protein synthesis in the rumen but that 65% of the protozoa die and are degraded in the rumen.

Abomasum↗
PubMed1999

A combinatorial ledge: reverse transcriptase fidelity, total body viral burden, and the implications of multiple-drug HIV therapy for the evolution of antiviral resistance.

The chronicity, high mutation rates, and high circulating titers of HIV during the 'stable' phase of infection make rapid evolution of resistance mutations a key predictor of antiretroviral efficacy. Recent advances in measurement of viral RNA titers, turnover dynamics and the in vivo spectrum of resistance mutations allow realistic in vivo estimates of important kinetic parameters of within-patient evolution of viral resistance. First-order estimates of the frequency of viral genotypes necessary for resistance to many antiretroviral combination regimens indicate that many such genotypes pre-exist in patients prior to initiation of therapy. The combinatorial nature of observed multiply-resistant genotypes, however, along with current estimates of total-body viral load and viral turnover dynamics, imply a strikingly sharp transition associated with the change from two-drug to three-drug antiretroviral regimens: pre-existing resistance being near-certain in the first instance but highly unlikely in the second. This abrupt change, a 'combinatorial ledge', carries with it a number of important implications for the understanding and control of HIV infection and other potential targets of antiviral therapy.

Anti-HIV Agents↗
PubMed1990

[Inhibitors of oncogene product functions].

Streptomyces and other microorganisms produce antibiotics, and enzyme inhibitors as secondary metabolites. Thus, they could be said as a treasury of organic compounds which have various structures and biological functions. Since oncogene theory has been extensively developed, we have screened oncogene function inhibitors from microorganisms as a new group of microbial secondary metabolites. Erbstatin is an inhibitor of epidermal growth factor (EGF) receptor and p60v-src-associated tyrosine kinase. Its inhibitory pattern vs. peptide is competitive. In cell culture it inhibited both EGF receptor autophosphorylation and internalization. Recently, we have isolated lavendustin A, an extremely potent inhibitor of tyrosine kinase, from Streptomyces. Lavendustin A is a novel compound and about 50 times stronger than erbstatin in inhibiting tyrosine kinase. Oxanosine is an inhibitor of ras oncogene product activity. It induces normal phenotypes in temperature-sensitive Kirsten sarcoma virus-infected rat kidney cells, lowering the intracellular levels of guanine nucleotides. Many oncogenes including src, ras, sis, fms and erbB are known to activate cellular phosphatidylinositol (PI) turnover. Therefore we have screened inhibitors of PI turnover and isolated psi-tectorigenine and pendolmycin from Nocardiopsis and inostamycin from Streptomyces. PI kinase is an enzyme involved in PI turnover pathways. We have isolated 2, 3-dihydroxybenzoic acid from Streptomyces as an inhibitor of PI kinase. These oncogene function inhibitors from microorganisms will be useful for the mechanistic study of oncogene product activities.

1-Phosphatidylinositol 4-Kinase↗
PubMed2004

Microbial degradation of chlorobenzene under oxygen-limited conditions leads to accumulation of 3-chlorocatechol.

Five bacterial strains (Acidovorax facilis B517, Cellulomonas turbata B529, Pseudomonas veronii B547, Pseudomonas veronii B549, and Paenibacillus polymyxa B550) isolated on chlorobenzene as the sole source of carbon and energy were screened for the accumulation of the putative metabolic intermediate 3-chlorocatechol during growth on chlorobenzene under oxygen-limited conditions in the presence and absence of nitrate (1 mM). 3-Chlorocatechol accumulated in the growth media of all five strains, but accumulation was significantly less in cultures of A. facilis B517 compared to the other four strains. The presence of nitrate did not influence the biological conversion pattern. However, biologically produced nitrite reacted with 3-chlorocatechol chemically, a reaction that masked the accumulation of 3-chlorocatechol. For P. veronii B549, a clear relationship between the presence of 3-chlorocatechol in the medium and low oxygen concentrations was demonstrated. The assumption is made that accumulation of 3-chlorocatechol is due to the low enzymatic turnover of the 3-chlorocatechol cleaving enzyme, catechol-1,2-dioxygenase, at low oxygen concentrations.

Bacteria↗
PubMed1986

Influence of macrophyte decomposition on growth rate and community structure of okefenokee swamp bacterioplankton.

Dissolved substances released during decomposition of the white water lily (Nymphaea odorata) can alter the growth rate of Okefenokee Swamp bacterioplankton. In microcosm experiments dissolved compounds released from senescent Nymphaea leaves caused a transient reduction in the abundance and activity of water column bacterioplankton, followed by a period of intense bacterial growth. Rates of [H]thymidine incorporation and turnover of dissolved d-glucose were depressed by over 85%, 3 h after the addition of Nymphaea leachates to microcosms containing Okefenokee Swamp water. Bacterial activity subsequently recovered; after 20 h [H]thymidine incorporation in leachate-treated microcosms was 10-fold greater than that in control microcosms. The recovery of activity was due to a shift in the composition of the bacterial population toward resistance to the inhibitory compounds present in Nymphaea leachates. Inhibitory compounds released during the decomposition of aquatic macrophytes thus act as selective agents which alter the community structure of the bacterial population with respect to leachate resistance. Soluble compounds derived from macrophyte decomposition influence the rate of bacterial secondary production and the availability of microbial biomass to microconsumers.

Journal Article↗
PubMed1989

Inhibition of Vibrio harveyi bioluminescence by cerulenin: in vivo evidence for covalent modification of the reductase enzyme involved in aldehyde synthesis.

Bacterial bioluminescence is very sensitive to cerulenin, a fungal antibiotic which is known to inhibit fatty acid synthesis. When Vibrio harveyi cells pretreated with cerulenin were incubated with [3H]myristic acid in vivo, acylation of the 57-kilodalton reductase subunit of the luminescence-specific fatty acid reductase complex was specifically inhibited. In contrast, in vitro acylation of both the synthetase and transferase subunits, as well as the activities of luciferase, transferase, and aldehyde dehydrogenase, were not adversely affected by cerulenin. Light emission of wild-type V. harveyi was 20-fold less sensitive to cerulenin at low concentrations (10 micrograms/ml) than that of the dark mutant strain M17, which requires exogenous myristic acid for luminescence because of a defective transferase subunit. The sensitivity of myristic acid-stimulated luminescence in the mutant strain M17 exceeded that of phospholipid synthesis from [14C]acetate, whereas uptake and incorporation of exogenous [14C]myristic acid into phospholipids was increased by cerulenin. The reductase subunit could be labeled by incubating M17 cells with [3H]tetrahydrocerulenin; this labeling was prevented by preincubation with either unlabeled cerulenin or myristic acid. Labeling of the reductase subunit with [3H]tetrahydrocerulenin was also noted in an aldehyde-stimulated mutant (A16) but not in wild-type cells or in another aldehyde-stimulated mutant (M42) in which [3H]myristoyl turnover at the reductase subunit was found to be defective. These results indicate that (i) cerulenin specifically and covalently inhibits the reductase component of aldehyde synthesis, (ii) this enzyme is partially protected from cerulenin inhibition in the wild-type strain in vivo, and (iii) two dark mutants which exhibit similar luminescence phenotypes (mutants A16 and M42) are blocked at different stages of fatty acid reduction.

Acylation↗
PubMed1991

femA, which encodes a factor essential for expression of methicillin resistance, affects glycine content of peptidoglycan in methicillin-resistant and methicillin-susceptible Staphylococcus aureus strains.

femA is a chromosomally encoded factor, occurring naturally in Staphylococcus aureus, which is essential for the expression of high-level methicillin resistance in this organism. The production of a low-affinity penicillin-binding protein, PBP2a or PBP2', which is intimately involved with methicillin resistance in S. aureus, is not influenced by femA. To elucidate a possible physiological function of the 48-kDa protein encoded by femA, several related methicillin-resistant, methicillin-susceptible, and Tn551 insertionally inactivated femA mutants were analyzed for possible changes in cell wall structure and metabolism. Independent of the presence of mec, the methicillin resistance determinant, all femA mutants had a reduced peptidoglycan (PG) glycine content (up to 60% in the molar ratio of glycine/glutamic acid) compared to that of related femA+ parent strains. Additional effects of femA inactivation and the subsequent decrease in PG-associated glycine were (i) reduced digestion of PG by recombinant lysostaphin, (ii) unaltered digestion of PG by Chalaropsis B-muramidase, (iii) reduced cell wall turnover, (iv) reduced whole-cell autolysis, and (v) increased sensitivity towards beta-lactam antibiotics. Also, the PG-associated glycine content of a femA::Tn551 methicillin-susceptible strain was restored concomitantly with the methicillin resistance to a level almost equal to that of its femA+ methicillin-resistant parent strain by introduction of plasmid pBBB31, encoding femA.

Acetylglucosamine↗
PubMed1987

Changes in collagen metabolism and proteinolysis after repeated inhalation exposure to ozone.

To study the changes in collagen metabolism that occur in the pathogenesis of pulmonary fibrosis, female rats were exposed to 0, 0.57, and 1.1 ppm ozone for 19 hr/day for 11 days and sacrificed 12 or 60 days after initiation of exposure. The lungs of rats sacrificed at 12 days after initiation of exposure to 1.1 ppm had interstitial pneumonia characterized by a mixed inflammatory cell infiltrate, type II cell hyperplasia, and fibroplasia, a proliferation of the collagen-producing cells; increased cathepsin D and macrophage elastase activity, indicating macrophage-induced proteinolysis; a reduced percentage of the increased collagen production that was ultrafilterable, indicating a decreased rate of intracellular degradation of newly produced collagen prior to its secretion; and increased lavage fluid hydroxyproline, indicating turnover of extracellular collagenous matrix. Reduced intracellular collagen degradation correlated directly with both increased net collagen production and fibroplasia in rats exposed to 1.1 ppm ozone for 11 days. These changes preceded an increased total lung collagen and the development of modest fibroplasia and fibrosis in the alveolar duct regions by 60 days after the 1.1 ppm ozone exposure was initiated.

Animals↗
PubMed1990

Inhibition of the bacteriolytic effect of beta-lactam-antibiotics on Staphylococcus aureus by the polyanionic drugs suramin and Evans Blue.

The anionic polyelectrolytes suramin and Evans Blue inhibited different autolytic systems involved in wall growth and wall turnover of growing staphylococci and in wall autolysis of resting bacteria. Moreover, both substances lowered the beta-lactam-induced pre-lytic release of cytoplasmic constituents from staphylococci, and inhibited the beta-lactam-induced bacteriolysis as well as the loss of viability. The protective effects of these sulfonated drugs against bacteriolysis were also monitored by electron microscopy. Some medical implications of our results are discussed.

Anti-Bacterial Agents↗
PubMed1994

HIV-1 drug resistance. Molecular pathogenesis and laboratory monitoring.

Molecular and clinical aspects of HIV-1 pathogenesis are described, including the turnover of the HIV-1 population in vivo, the clinical significance of resistance to HIV-1 reverse transcriptase (RT) inhibitors, and the inter-relationship between virus replication and RT inhibitor resistance. The molecular genetics of RT inhibitor resistance, including interactive effects of different RT mutations and the implications of those effects for combination chemotherapy, are summarized. Structural studies of RT and the biochemical bases of drug resistance are discussed.

Acquired Immunodeficiency Syndrome↗
PubMed2004

Lipopolysaccharide needs soluble CD14 to interact with TLR4 in human monocytes depleted of membrane CD14.

Toll-like receptors recognize specific patterns of microbial components and regulate the activation of both innate and adaptive immunity. TLR4 recognizes lipopolysaccharide (LPS) in monocytes/macrophages with the help of other molecules like CD14 and MD-2, which indicates that the functional LPS receptor forms a large complex. The functional relationship between the components has been the subject of debate, as have the modifications induced by the ligand in the expression of some of these components. Moreover, as for other members of this family of receptors, the possible direct interaction of receptors and their ligands is a matter of discussion. In this paper we address the question of whether the expression of some of the components influences the expression of the rest. Human monocytes in which CD14 has been downregulated through interference in the turnover of the molecule at the Golgi level, show normal membrane TLR4 expression, when compared with control cells. On the other hand, LPS alters membrane TLR4 expression by monocytes devoid of membrane CD14 only in the presence of human serum. The effect of serum is blocked by anti-CD14 monoclonal antibodies, which strongly suggests a functional role for soluble CD14/LPS complexes in the interaction with TLR4. Our data add information on the relationship between the components of the LPS receptor and the characteristics of the interaction of LPS and TLR4 in cells devoid of membrane CD14.

Adult↗
PubMed2000

In vivo dynamics and pathogenicity of wild-type and resistant Hepatitis B virus during long-term lamivudine monotherapy - a clinical note.

BACKGROUND: Genotypic resistance of Hepatitis B virus (HBV) against lamivudine evolves within months after onset of therapy. OBJECTIVES: To determine the longitudinal order in which resistance mutations appear and to compare the kinetics and pathogenicity of wild-type and resistant HBV. STUDY DESIGN: In a longitudinal study, consecutive samples were drawn over a period of 28 months from a patient with chronic hepatitis B, and resistance mutations were followed by sequencing a part of the polymerase region of HBV. These data were compared with HBV copy numbers, HBsAg and ALT levels, and results of consecutive liver biopsies. RESULTS: After 21 weeks of treatment, a silent mutation at codon 528 (CTG to TTG) occurred. Significant genotypic resistance was detectable after 68 weeks, indicated by a substitution of isoleucine for methionine at residue 552 (M552I). Nineteen weeks later, the virus exhibited additional resistance-associated mutations (L528M and I552V). The resulting high-level resistance was reflected by an increase of serum HBV copies of 4.7 log(10). The turnover of wild-type and resistant HBV was 2.6x10(6) and 1.8x10(6) virions/day, respectively. HBsAg and ALT levels were lower within the period when resistant HBV was detectable. During treatment the progress of liver fibrosis was arrested. CONCLUSIONS: The in vivo replicative capacities and dynamics of wild-type and resistant HBV were similar. However, resistant HBV seemed to exhibit reduced pathogenicity.

Base Sequence↗
PubMed2002

Utilization of xylitol dehydrogenase in a combined microbial/enzymatic process for production of xylitol from D-glucose.

The production of xylitol from D-glucose occurs through a three-step process in which D-arabitol and D-xylulose are formed as the first and second intermediate product, respectively, and both are obtained via microbial bioconversion reactions. Catalytic hydrogenation of D-xylulose yields xylitol; however, it is contaminated with D-arabitol. The aim of this study was to increase the stereoselectivity of the D-xylulose reduction step by using enzymatic catalysis. Recombinant xylitol dehydrogenase from the yeast Galactocandida mastotermitis was employed to catalyze xylitol formation from D-xylulose in an NADH-dependent reaction, and coenzyme regeneration was achieved by means of formate dehydrogenase-catalyzed oxidation of formate into carbon dioxide. The xylitol yield from D-xylulose was close to 100%. Optimal productivity was found for initial coenzyme concentrations of between 0.5 and 0.75 mM. In the presence of 0.30 M (45 g/L) D-xylulose and 2000 U/L of both dehydrogenases, exhaustive substrate turnover was achieved typically in a 4-h reaction time. The enzymes were recovered after the reaction in yields of approx 90% by means of ultrafiltration and could be reused for up to six cycles of D-xylulose reduction. The advantages of incorporating the enzyme-catalyzed step in a process for producing xylitol from D-glucose are discussed, and strategies for downstream processing are proposed by which the observed coenzyme turnover number of approx 600 could be increased significantly.

Arthrobacter↗
PubMed1998

Homologs of the vancomycin resistance D-Ala-D-Ala dipeptidase VanX in Streptomyces toyocaensis, Escherichia coli and Synechocystis: attributes of catalytic efficiency, stereoselectivity and regulation with implications for function.

BACKGROUND: Vancomycin-resistant enterococci are pathogenic bacteria that have altered cell-wall peptidoglycan termini (D-alanyl-D-lactate [D-Ala-D-lactate] instead of D-alanyl-D-alanine [D-Ala-D-Ala]), which results in a 1000-fold decreased affinity for binding vancomycin. The metallodipeptidase VanX (EntVanX) is key enzyme in antibiotic resistance as it reduces the cellular pool of the D-Ala-D-Ala dipeptide. RESULTS: A bacterial genome search revealed vanX homologs in Streptomyces toyocaensis (StoVanX), Escherichia coli (EcoVanX), and Synechocystis sp. strain PCC6803 (SynVanX). Here, the D,D-dipeptidase catalytic activity of all three VanX homologs is validated, and the catalytic efficiencies and diastereoselectivity ratios for dipeptide cleavage are reported. The ecovanX gene is shown to have an RpoS (sigma(s))-dependent promoter typical of genes turned on in stationary phase. Expression of ecovanX and an associated cluster of dipeptide permease genes permitted growth of E. coli using D-Ala-D-Ala as the sole carbon source. CONCLUSIONS: The key residues of the EntVanX active site are strongly conserved in the VanX homologs, suggesting their active-site topologies are similar. StoVanX is a highly efficient D-Ala-D-Ala dipeptidase; its gene is located in a vanHAX operon, consistent with a vancomycin-immunity function. StoVanX is a potential source for the VanX found in gram-positive enterococci. The catalytic efficiencies of D-Ala-D-Ala hydrolysis for EcoVanX and SynVanX are 25-fold lower than for EntVanX, suggesting they have a role in cell-wall turnover. Clustered with the ecovanX gene is a putative dipeptide permease system that imports D-Ala-D-Ala into the cell. The combined action of EcoVanX and the permease could permit the use of D-Ala-D-Ala as a bacterial energy source under starvation conditions.

Amino Acid Sequence↗