Biological ensiling of sugarcane tops. VII. Isolation and characteristics of lactic acid bacteria.
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Animal Feed↗
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Ester synthesis in an aqueous environment by Streptococcus thermophilus and other dairy lactic acid bacteria.
The ability of Streptococcus thermophilus ST1 and 19 other dairy lactic acid bacteria (LAB) to synthesize esters was investigated in an aqueous environment. These LAB were able to synthesize esters from alcohols and glycerides via a transferase reaction (alcoholysis) in which fatty acyl groups from glycerides were transferred to alcohols. S. thermophilus ST1 was active on tributyrin and on di- or monoglycerides of up to C10 with ethanol as the acyl acceptor. This strain was also active on a diglyceride of C6 and monoglyceride of C8 with 2-phenyl ethanol as the acyl acceptor. Alcoholysis occurred preferentially over hydrolysis. S. thermophilus ST1 had an apparent K(m) value of 250 mM for ethanol and an apparent K(m) value of 1.3 mM for tributyrin, measured against whole cells. Around 80% of both the transferase activity and the esterase activity were detected in the cell-free extract (CFE) of strain ST1. Both activities in the CFEs of five LAB tested were, to a similar degree, enhanced slightly by growth in the presence of ethanol and tributyrin. Using tributyrin and ethanol as substrates, the transferase activities ranged over 0.006-1.37 units/mg cell dry weight among the LAB tested and were both species- and strain-dependent.
Alcohols↗
The arginine deiminase locus of Oenococcus oeni includes a putative arginyl-tRNA synthetase ArgS2 at its 3'-end.
Oenococcus oeni is the most important lactic acid bacteria of the winemaking process involved in malolactic fermentation. Most O. oeni strains are able to catabolyze arginine via the arginine deiminase (ADI) pathway. The arcR, A, B, C, D1, and D2 cluster of O. oeni bacteria has been characterized. Here, we completed the ADI locus sequence. Downstream of arcD2 gene, we found an additional gene which encodes a putative arginyl-tRNA synthetase (argS2). It is not the same arginyl-tRNA synthetase which was sequenced in O. oeni MCW strain. Transcriptional analyses have shown that argS2 was induced by arginine. In addition, systematic polymerase chain reaction amplification of each arc gene and argS2 has provided a characteristic feature of the ADI locus within the O. oeni species: all genes of ADI locus are present or absent according to the strains.
Amino Acyl-tRNA Synthetases↗
Intraspecific diversity of Oenococcus oeni strains determined by sequence analysis of target genes.
Using molecular techniques and sequencing, we studied the intraspecific diversity of Oenococcus oeni, a lactic acid bacterium involved in red winemaking. A relationship between the phenotypic and genotypic characterization of 16 O. oeni strains isolated from wine with different levels of enological potential was shown. The study was based on the comparative genomic analysis by subtractive hybridization between two strains of O. oeni with opposite enological potential. The genomic sequences obtained from subtractive hybridization were amplified by polymerase chain reaction and sequenced for the 16 strains. A considerable diversity among strains of O. oeni was observed.
Base Sequence↗
Survival of lactic acid bacteria in seawater: a factorial study.
A feasibility study of lactic bacteria as potential probiotics in larval cultures of marine fish was performed by investigating the survival of five strains of lactic bacteria in seawater by readily standardized procedures at different temperatures and salinities. These conditions were chosen in such a way that their combinations define a complete first-order factorial design. Depending on the strain and the ambient conditions, the survival adhered to first-order kinetics in some cases, and to the Gompertz equation in others. The half lives (t0.5) calculated from these models were subsequently introduced as responses to the factorial designs, estimating the coefficients of empirical equations that describe the group effect of temperature and salinity on t0.5. Simply additive effects were found in two cases, a negative first-order interaction in another case, while another two required second-order models.
Colony Count, Microbial↗
Growth response and modifications of organic nitrogen compounds in pure and mixed cultures of lactic acid bacteria from wine.
The interactions between the proteolytic X2L strain of Oenococcus oeni and the non-proteolytic 12p strain of Pediococcus pentosaceus were assayed. The characteristics of cell growth, protein degradation, and amino acid production of both strains were determined in pure and mixed cultures. O. oeni showed poor cell growth and greater ability in the release of amino acids to the extracellular medium, whereas P. pentosaceus showed a higher yield in cell production with a decrease in the amino acid concentration in the medium. P. pentosaceus especially consumed essential amino acids for growth, and O. oeni released several of the essential amino acids important for growth of P. pentosaceus. In the mixed culture, mutualism was observed. The higher activity of the proteolytic system of O. oeni in mixed culture produced an increase in cell growth and in the amount of essential amino acids released. These findings provide new knowledge about the metabolic interactions between lactic acid bacteria isolated from wine when proteins are degraded in mixed bacterial populations.
Amino Acids↗
Comparison of bacteriocins produced by lactic-acid bacteria isolated from boza, a cereal-based fermented beverage from the Balkan Peninsula.
Boza is a low-pH and low-alcohol cereal-based beverage produced in the Balkan Peninsula. From a total population of 9 x 10(6) colony-forming units ml(-1), four isolates (JW3BZ, JW6BZ, JW11BZ, and JW15BZ) produced bacteriocins active against a broad spectrum of Gram-positive bacteria. Bacteriocin JW15BZ inhibited the growth of Klebsiella pneumoniae. The producer strains were identified as Lactobacillus plantarum (strains JW3BZ and JW6BZ) and L. fermentum (strains JW11BZ and JW15BZ). The spectrum of antimicrobial activity, characteristics, and mode of action of these bacteriocins were compared with bacteriocins previously described for lactic-acid bacteria isolated from boza.
Anti-Bacterial Agents↗
Behavior of variable V3 region from 16S rDNA of lactic acid bacteria in denaturing gradient gel electrophoresis.
Separation of amplified V3 region from 16S rDNA by denaturing gradient gel electrophoresis (DGGE) was tested as a tool for differentiation of lactic acid bacteria commonly isolated from food. Variable V3 regions of 21 reference strains and 34 wild strains referred to species belonging to the genera Pediococcus, Enterococcus, Lactococcus, Lactobacillus, Leuconostoc, Weissella, and Streptococcus were analyzed. DGGE profiles obtained were species-specific for most of the cultures tested. Moreover, it was possible to group the remaining LAB reference strains according to the migration of their 16S V3 region in the denaturing gel. The results are discussed with reference to their potential in the analysis of LAB communities in food, besides shedding light on taxonomic aspects.
DNA, Bacterial↗
Characterization, production, and purification of carnocin H, a bacteriocin produced by Carnobacterium 377.
Carnocin H, a bacteriocin produced by a Carnobacterium sp., inhibited lactic acid bacteria, clostridia, enterococci, and some Staphylococcus aureus strains. Some strains of Listeria and Pediococcus were also sensitive to carnocin H. The bacteriocin was produced during the late stationary growth phase. Carnocin H was purified by cation exchange chromatography and reverse phase chromatography. Amino acid sequence and composition indicate that carnocin H is a novel bacteriocin belonging to the class II bacteriocins. The bacteriocin consists of approximately 75 amino acid residues with a highly cationic N-terminal containing six succeeding lysines. Activity, as measured by agar diffusion zones, was reduced at increased pH values, levels of indicator bacteria, NaCl, agar, and soy oil.
Amino Acid Sequence↗
Carnocin KZ213 produced by Carnobacterium piscicola 213 is adsorbed onto cells during growth. Its biosynthesis is regulated by temperature, pH and medium composition.
Carnocin KZ213 is an antilisterial bacteriocin produced by Carnobacterium piscicola 213. The effects of pH and temperature were studied during batch fermentation in MRS* medium (modified MRS without ammonium citrate or sodium acetate). The optimal pH for growth is between 6 and 7. The maximum bacteriocin productivity in the supernatant occurs at pH 7. Operating at controlled pH increases the volumetric activity of the free bacteriocin by 8- to 16-fold, compared with uncontrolled pH. No bacteriocin production is observed below pH 6.5. Temperature has a dramatic effect on carnocin KZ213 production. Growth is optimal at 25 degrees C and 30 degrees C, although no bacteriocin production is detected at 30 degrees C. Also, bacteriocin production is observed at 25 degrees C in MRS*, but not in complex APT broth, where growth is optimal. The presence of glucose as a carbon and/or energy source is important for carnocin KZ213 synthesis. Hence, bacteriocin synthesis is regulated by temperature, carbon source and medium composition. Quantification studies of bacteriocin adsorbed onto producer cells show that the majority of the carnocin KZ213 secreted is adsorbed onto the producer cells during growth. Only 15% of the total bacteriocin produced is detected in the cell-free supernatant at the end of growth.
Bacteriocins↗
The effect of cadmium on the normal tooth fissure plaque flora of Sprague-Dawley rats.
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Actinomycetaceae↗
Phosphofructokinases from Lactobacteriaceae. II. Purification and properties of phosphofructokinase from Streptococcus thermophilus.
Phosphofructokinase (ATP : D-fructose-6-phosphate 1-phosphotransferase, EC 2.7.1.11) from Streptococcus thermophilus has been purified. It is a tetramer composed of identical subunits of molecular weight 36 000 and exhibits Michaelis-Menten kinetics. Compared to the phosphofructokinases from taxonomically related bacteria, the enzyme from S. thermophilus is more stable at high temperatures. In addition, it has been demonstrated that the phosphofructokinases from lactobacteria and also from Bacillus stearothermophilus show immunologic cross-reaction. In spite of the significantly different kinetic properties and the different thermostability of these enzymes, this finding indicates great structural resemblance.
Geobacillus stearothermophilus↗
Problems of microbial ecology in man space mission.
The state of microflora should be considered as one of the important links in chain of the specific functional disorders involving the spaceflight factors effects. At the same time, there occurs an establishment of nonspecific disbiotic response of the human microflora in the space flights of various duration characterized by a decrease up to a reduction of the "defense" group of microorganisms; by an appearance of unusual microorganisms in various biotypes, by accumulation of the potential of pathogenic species of automicroflora with their succeeding colonization and long term persistence. In experimental animal models to simulate dysbacteriosis and with the use of SPF-rats and primates flow aboard Cosmos biosatellites, the significance of indigenous microflora for preserving microecological homeostasis. Theoretically based and experimentally proven need for increasing the colonization resistance is confirmed by the practical use of the measures to stabilize microflora of the cosmonauts during space flights.
Animals↗
Lactic acid and pH as indicators of spoilage for vacuum-packed cooked ring sausages.
Lactic acid production and pH changes of 206 vacuum-packed cooked ring sausages stored at 2, 4 and 12 degrees C from 21 different production runs were monitored as a function of time and of microbial growth. The total lactic acid concentrations and pH values were first at a constant level, starting to increase sharply after the lactobacilli count reached about 5 x 10(7) or 6 x 10(7) cfu/g, respectively. The lactic acid and pH changes as a function of the lactobacilli count were similar at 4 and 12 degrees C. The sharp increase at high lactobacilli counts was observed in both L-lactic acid and D-lactic acid. The variation was lesser and the increase greater in D-lactic acid formation than in L-lactic acid. Above a level of 3-4 mg lactic acid/g most of the samples were deemed unfit. The pH started to decrease from a level of approx. 6.3; below 5.8-5.9 the samples were deemed unfit. The lowest pH value observed was 4.58. Both a high lactic acid content and a low pH indicated that the sausage was spoiled. These changes, however, took place at later stages of storage, and do not give information about the early phase of spoilage.
Animals↗
Use of low molecular mass RNA profiles to identify lactic acid bacteria and related organisms associated with foods.
Fourteen strains of lactic acid bacteria and species of Brochothrix, Carnobacterium, Enterococcus, Erysipelothrix, Kurthia and Listeria were examined using low molecular mass RNA (5S rRNA and tRNA) profiles. These profiles were developed on denaturing polyacrylamide gels. Gel strengths between 9 and 14% were tested to improve resolution of distinct bands for densitometrical analysis. Profiles generated on 12% gels proved to be the best for scanning. Scans of class 2 tRNAs by densitometry showed a characteristic profile for each genus. In the case of Lactobacillus each species studied gave a unique profile. The technique of low molecular mass RNA profiling may provide a useful means for identifying different bacteria from ecosystems such as meats.
Culture Media↗
Ropy slime-producing lactic acid bacteria contamination at meat processing plants.
At three Finnish meat processing plants the processing rooms, meat trimmings and carcasses were examined for the presence of ropy slime-producing lactic acid bacteria. Bacterial isolates similar to ropy slime-producing lactobacilli strains able to produce ropy slime on meat products, were recovered from the processing rooms and meat trimmings, indicating that these rooms and raw materials are a source of contamination for ropy bacteria. The ability to produce ropy slime would appear to be a common characteristic of lactobacilli, since altogether 10 different ropy lactobacilli groups were isolated in this study.
Air Microbiology↗
Microbial ecology of fresh pork stored under modified atmosphere at -1, 4.4 and 10 degrees C.
The prevalent bacteria on fresh pork packaged in modified atmosphere with elevated CO2 were determined by selection of representative colonies from the greatest dilution of meat samples. The pork samples were stored in two packaging films of different oxygen permeability at three storage temperatures. Strains were classified and those identified as lactic acid bacteria were screened for production of inhibitory substances. The types of bacteria isolated from samples stored in the two packaging films were similar. Storage temperature influenced the type of bacteria that dominated the microbial population. At 10 degrees C the prevalent microflora consisted of aeromonads, Enterobacteriaceae and lactic acid bacteria but at 4.4 and -1 degrees C, aeromonads, Brochothrix thermosphacta and lactic acid bacteria dominated. Listeriae were detected as part of the prevalent microflora on samples stored at -1 degree C, but not on samples stored at 4.4 or 10 degrees C. Species of lactic acid bacteria dominating the microflora were influenced by growth medium. The majority of isolates taken from Plate Count agar were carnobacteria whereas those from Lactobacilli MRS agar were homofermentative lactic acid bacteria. Of the 538 lactic acid bacteria isolates screened for production of inhibitory substances, 162 strains showed deferred inhibition toward a range of lactic acid bacteria and nonlactic acid bacteria indicator strains.
Animals↗
Bacteriocin production by Carnobacterium piscicola LV 61.
Carnobacterium piscicola LV 61 produces a bacteriocin designated piscicolin 61, that is heat resistant, active over a wide pH range and inactivated by alpha-chymotrypsin, pepsin, trypsin and papain. It is effective against strains of the genera Carnobacterium, Enterococcus and Listeria. Other lactic acid bacteria tested were less sensitive or resistant to piscicolin. It is produced at temperatures from 1 to 30 degrees C. Maximum bacteriocin activity was detected after the culture had entered the stationary phase of growth and when the culture was grown in a medium with an initial pH between 8.0 and 9.0. The same high amounts of bacteriocin could be obtained in a culture at a constant pH of 6.5. No bacteriocin was produced at pH 5.0. Peptone in the growth medium promotes bacteriocin production, whereas meat and yeast extract did not influence the amounts of bacteriocin produced. Bacteriocin production and immunity are probably encoded by a 22 kb plasmid.
Animals↗