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Acid Bacterium (acid + bacterium)
Kinds of Acid Bacterium Selected AbstractsThe chitinolytic system of Lactococcus lactis ssp. lactis comprises a nonprocessive chitinase and a chitin-binding protein that promotes the degradation of ,- and ,-chitinFEBS JOURNAL, Issue 8 2009Gustav Vaaje-Kolstad It has recently been shown that the Gram-negative bacterium Serratia marcescens produces an accessory nonhydrolytic chitin-binding protein that acts in synergy with chitinases. This provided the first example of the production of dedicated helper proteins for the turnover of recalcitrant polysaccharides. Chitin-binding proteins belong to family 33 of the carbohydrate-binding modules, and genes putatively encoding these proteins occur in many microorganisms. To obtain an impression of the functional conservation of these proteins, we studied the chitinolytic system of the Gram-positive Lactococcus lactis ssp. lactis IL1403. The genome of this lactic acid bacterium harbours a simple chitinolytic machinery, consisting of one family 18 chitinase (named LlChi18A), one family 33 chitin-binding protein (named LlCBP33A) and one family 20 N -acetylhexosaminidase. We cloned, overexpressed and characterized LlChi18A and LlCBP33A. Sequence alignments and structural modelling indicated that LlChi18A has a shallow substrate-binding groove characteristic of nonprocessive endochitinases. Enzymology showed that LlChi18A was able to hydrolyse both chitin oligomers and artificial substrates, with no sign of processivity. Although the chitin-binding protein from S. marcescens only bound to ,-chitin, LlCBP33A was found to bind to both ,- and ,-chitin. LlCBP33A increased the hydrolytic efficiency of LlChi18A to both ,- and ,-chitin. These results show the general importance of chitin-binding proteins in chitin turnover, and provide the first example of a family 33 chitin-binding protein that increases chitinase efficiency towards ,-chitin. [source] The effect of carbon and nitrogen sources on bovicin HC5 production by Streptococcus bovis HC5JOURNAL OF APPLIED MICROBIOLOGY, Issue 1 2009A.A.T. De Carvalho Abstract Aims:, To investigate the effect of media composition and agroindustrial residues on bovicin HC5 production by Streptococcus bovis HC5. Methods and Results:, Batch cultures of S. bovis HC5 were grown in basal medium containing different carbon and nitrogen sources. The activity of cell-free and cell-associated bovicin HC5 was determined in culture supernatants and acidic extracts obtained from cell pellets, respectively. Streptococcus bovis HC5 produced bovicin using a variety of carbon and nitrogen sources. The highest specific activity was obtained in media containing 16 g l,1 of glucose, after 16 h of incubation. The peak in cell-free and cell-associated bovicin HC5 activity was detected when S. bovis HC5 cultures reached stationary phase. The bovicin HC5 specific activity and bacterial cell mass increased approximately 3-fold when yeast extract and trypticase (0·5 and 1·0 g l,1, respectively) were added together to the basal medium. Streptococcus bovis HC5 cultures produced bovicin HC5 in cheese whey and sugar cane juice and maximal volumetric productivity was obtained after 12 h of incubation. Conclusions:,Streptococcus bovis HC5 is a versatile lactic acid bacterium that can utilize several carbon and nitrogen sources for bovicin HC5 production. This bacterium could be a useful model to study bacteriocin production in the rumen ecosystem. Significance and Impact of the Study:, The use of agroindustrial residues as carbon sources could have an economical impact on bovicin HC5 production. To our knowledge, this is the first report to show the use of sugar cane juice for bacteriocin production by lactic acid bacteria. [source] Identification of the agent from Lactobacillus plantarum KFRI464 that enhances bacteriocin production by Leuconostoc citreum GJ7JOURNAL OF APPLIED MICROBIOLOGY, Issue 6 2007J.Y. Chang Abstract Aim:, To provide evidence that the production of bacteriocin by lactic acid bacteria can be enhanced by the presence of a bacteriocin-sensitive strain and identify the agent that is responsible for enhancing bacteriocin production. Methods and Results:, One bacteriocin-producing lactic acid bacterium was isolated from kimchi. The strain GJ7 was designated as Leuconostoc citreum GJ7 based on Gram staining, biochemical properties, and 16S rRNA gene sequencing. The isolate produced a heat- and pH-stable bacteriocin (kimchicin GJ7), which has antagonistic activity against a broad spectrum of micro-organisms. Tricine-sodium dodecyl sulfate-polyacrylamide gel electrophoresis of purified kimchicin GJ7 showed a single band of molecular weight c. 3500 Da. Cultures of Leuc. citreum GJ7 in the presence of thermally inactivated kimchicin GJ7-sensitive strains, Lactobacillus plantarum KFRI 464, Lactobacillus delbrueckii KFRI 347, or Leuconostoc mesenteroides KCTC 1628, increased bacteriocin production. This inducing factor was characterized and purified from Lact. plantarum KFRI 464, which showed the greatest enhancement of kimchicin GJ7 activity. The inducing factor was purified using a DEAE (diethyl aminoethyl)-Sephacel column and high-performance liquid chromatography, and yielded a single band of c. 6500 Da. N -terminal sequencing of the inducing factor identified 16 amino acids. The N -terminal sequence of the inducing factor was synthesized and examined for the induction of kimchicin GJ7 activity, and was found to induce activity, but at a level about 10% lower than that of the entire molecule. Conclusions:, The presence of a bacteriocin-sensitive strain, Lact. plantarum KFRI 464, acts as an environmental stimulus to activate the production of kimchicin GJ7 by Leuc. citreum GJ7. The inducing factor from Lact. plantarum KFRI 464 is highly homologous to the 30S ribosomal protein S16 from various micro-organisms. The N -terminal sequence of the inducing factor examined in this study is a very important sequence related to the inducing activity. Nevertheless, the inducing factor may not be part of the ribosomal protein S16 itself. Significance and Impact of the Study:, We believe that the present study is the first to identify an agent that is produced by one micro-organism and influences bacteriocin production in another. The bacteriocin-enhancing system described in this study could be effectively used to control the growth of other micro-organisms (sensitive cells) in food systems. Moreover, this enhancement of bacteriocin production can be applied usefully in industrial production of natural food preservatives. [source] Reduction of Microflora of Whole Pickling Cucumbers by BlanchingJOURNAL OF FOOD SCIENCE, Issue 8 2000F. Breidt ABSTRACT: There is increasing interest in developing methods to control the presence of pathogenic and spoilage microorganisms on fresh fruits and vegetables. Blanching whole pickling cucumbers for 15 s at 80 °C reduced microbial cell counts by 2 to 3 log cycles from an initial population of typically 106 CFU/g. Vegetative microorganisms survived this blanching process (10,fold greater in number than the spore count), presumably because they were located beneath the surface of the cucumber. The sensitivity to heat of selected populations was measured by determining D values for pooled microorganisms (termed D values) isolated from fresh cucumbers. The Enterobacteriaceae population and the total aerobic microflora had similar Dp values to each other and to the D value for a selected lactic acid bacterium. [source] The effect of low pH on protein expression by the probiotic bacterium Lactobacillus reuteriPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 8 2008KiBeom Lee Dr. Abstract The ability of a lactic acid bacterium to survive passage through the gastrointestinal tract is a key point in its function as a probiotic. In this study, protein synthesis by the probiotic bacterium, Lactobacillus reuteri, was analyzed under transiently decreased pH conditions. L. reuteri cells grown to the midexponential growth phase at 37°C were exposed to transient (1,h) low-pH stresses from pH,6.8 to pH,5.0, 4.5, or 4.0. 2-DE allowed us to identify 40 common proteins that were consistently and significantly altered under all three low-pH conditions. PMF was used to identify these 40 proteins, and functional annotation allowed them to be distributed to six major classes: (i) transport and binding proteins; (ii) transcription,translation; (iii) nucleotide metabolism and amino acid biosynthesis; (iv) carbon energy metabolism; (v) pH homeostasis and stress; and (vi) unassigned. These findings provide new insight into the inducible mechanisms underlying the capacity of gastrointestinal L. reuteri to tolerate acid stress. [source] Bacteriocin production of probiotic Lactobacillus gasseri LA39 isolated from human feces in milk-based mediaANIMAL SCIENCE JOURNAL, Issue 5 2008Kensuke ARAKAWA ABSTRACT The use of bacteriocins from Lactobacillus gasseri, a probiotic lactic acid bacterium, as bio-preservatives in the food industry and animal formulations has been limited because few strains of Lb. gasseri are cultivated and produce a bacteriocin in natural media such as milk and milk-based media. By the determination of the growth-supplements to milk among the 47 nutrients, Lb. gasseri JCM1131T, LA39 and LA158 isolated from human feces were successfully cultured in reconstituted skim milk and cheese whey using proteose peptone as a nutrient supplement, where Lb. gasseri LA39 produced a useful bacteriocin, gassericin A, with effective growth-inhibiting activity against Gram-positive food-borne pathogens. The data suggest these developed low-cost safe media supporting enough production of bacteriocins by the probiotic Lb. gasseri LA39 could be used to improve the safe bio-preservation of foods and therapy of bovine mastitis, and extra cheese whey produced by cheese making industry is reused in the cultivation for probiotics effectively. [source] | |||||||||||||