Lipoquinones of some spore-forming rods, lactic-acid bacteria and actinomycetes.

The respiratory quinones of 73 strains of Gram-positive bacteria including spore-forming rods, lactic-acid bacteria and actinomyctes were examined. Menaquinones with seven isoprenoid units (MK-7) were the main quinone type found in representatives of the genus Bacillus and in Sporolactobacillus inulinus. However, a strain of B. thuringiensis produced MK-8 in addition to MK-7, and strains of B. lentus and B. pantothenticus appeared to produce MK-9 and MK-8, respectively, with no MK-7. In the clostridia and lactic-acid bacteria, no quinones were found, except in Pediococcus cerevisiae NCTC 8066 and Lactobacillus casei subsp. rhamnosus ATCC 7469, which contained menaquinones, and Streptococcus faecalis NCTC 775 and HIM 478-1, which contained demethylmenaquinones, in relatively low concentrations. Menaquinones were also found in the actinomycetes (except Actinomyces odontolyticus and Bifidobacterium bifidum which did not produce any quinones) and in Protaminobacter alboflavus ATCC 8458, the so-called Actinobacillus actinoides ATCC 15900 and Noguchia granulosis NCTC 10559.     

Fate of aflatoxin B-1 in fermented dairy products

Polyacrylamide gel electropheresis and thin layer chromatography (TLC) were applied to detect the fate of aflatoxin B-1 in milk fermented with an active culture of Streptococcus lactis (ATCC-11454).TLC analysis revealed the formation of two fluorescent metabolites (B₂a and R₀) in fermented milk.Electropheretic analysis of both casein and whey protein showed fluorescent bands in the region of Kappa-casien and immunoglobulin which are glycoproteins in nature. The transformation of B-1 to the nontoxic metabolite B₂a and the less toxic compound aflatoxicol (R₀) reflects the preference for fermented dairy products in consumption in order to reduce chances of toxicity.     

Effect of heat treatment on the proteolytic activity of mesophilic bacteria isolated from goats' milk cheese

Strains of mesophilic lactococci and lactobacilli isolated from goats' milk cheese were grown to maximum density in milk at 30°C, pH 6·5. They were subsequently cooled to 12°C and then heated at 50°, 52° and 54°C (holding time, 15 s). The micro-organisms tested were Lactococcus lactis subsp. lactis IFPL 60, IFPL 22 and IFPL 359, Lactobacillus casei subsp. casei IFPL 731 and Lactobacillus plantarum IFPL 3, isolated from raw goats' milk cheese. The heated cells presented lower viability and acidification capacity than unheated cells. After heat treatment at 50°C, all the test strains effected practically no reduction in pH of milk (6 h), except for Lactococcus lactis subsp. lactis IFPL 60, which reduced pH to 5·9 as compared to 4·9 attained by the unheated controls. After treatment, proteolytic, aminopeptidase and dipeptidase activities of cell-free extracts decreased to a lesser extent than the number of viable cells with acidifying ability. The results suggest that these strains, if treated at 50°C, may be suitable as extra sources of important ripening enzymes in cheese making.     

Thermophysiology of Streptococcus mutans and related lactic-acid bacteria

The temperature ranges for growth of Streptococcus mutans GS-5 and S. sobrinus 6715 were found to be very narrow, from about 30 to 47 °C, with optimal growth around 37 °C. Thus, the organisms showed little potential to grow in the environment outside of the animal host. In contrast wider ranges were found for Enterococcus hirae, S. rattus and S. sanguis. Detailed study of S. mutans GS-5 showed that energetic coupling, reflected in yields of biomass per mol of glucose utilized, were not greatly affected by changes in temperature within the growth range. However, since glycolysis occurred over a wider temperature range (about 10 to 52 °C) than growth, yield values dropped to zero at temperatures above or below the growth range. The temperature range for glycolysis could be related to temperature sensitivity of the phosphoenolpyruvate: sugar phosphotransferase system for sugar uptake. F-ATPases were active over a similar range of temperatures, but with a broad optimal range from about 30 to 50 °C. Proton permeability of S. mutans increased steadily with temperature in a manner similar to that of other mesophilic bacteria, such as Escherichia coli. Growth of the bacteria in media supplemented with various fatty acids had major effects on proton permeabilities but the effects were not well reflected by changes in growth or glycolysis of the bacteria. The overall conclusions were that S. mutans is a typical mesophile in relation to membrane and catabolic functions but its narrow temperature range for growth is related to temperature sensitivities of anabolic systems.     

Biological deacidification of wines using lactic-acid bacteria and yeasts

Based on a study of 200 lactic-acid bacteria monocultures and 30 associating lactic bacteria and yeasts cultures, a stable association was created formed by Leuconostoc oenos, Pediococcus pentosaceus and Saccharomyces cerevisiae yeasts, intended for the biological deacidification of wine. Physiology of microorganisms and their effect on the wine chemical composition was studied. By means of selective association, high quality fine wines were produced from the high-acid wines.     

Amidase activity of some bacteria

The amidase activity of bacteria possessing a high nitrilase activity was found to display the same spectrum although the bacteria may belong to different taxonomic groups,Bacillus, Bacteridium, Micrococcus, Brevibacterium. The spectrum of amidase activity, although very broad, is more restricted than that of nitrilase activity. Internal amides as well as vinyl-bound amides are not hydrolyzed.     

Environmental factors associated with proteolytic activity of estuarine bacteria

The effects of various parameters on the extracellular hydrolysis of protein by salt marsh bacteria were examined using an agar plate assay technique. Maximum activity was observed at pH 8 and 18 C. Elimination of salts and nutrients from the growth media had little effect on activity; while, incubation in a reduced oxygen atmosphere markedly restricted proteolysis by laboratory stocks and random isolates. The availability of oxygen appeared to be one of the important factors controlling extracellular protease production by salt marsh bacteria.     

Extracellular proteolytic activity of bacteria from soda-salt lakes of Transbaikalia

Influence of nitrogen source on proteinases synthesis in aerobic alkalotolerant and halotolerant bacteria from soda-salt lakes of Transbaikalia was studied. Maximal accumulation of proteinases was revealed on medium with peptones. Introduction of various sources of nitrogen in the medium did not result in increase of enzyme activity in cultural liquid. It was indicated that secreting proteinases of the studied bacteria strains possess narrow substrate specificity, hydrolyze proteins and n-nitroanilide substrates have maximal activity during GlpAALpNA hydrolysis. Data of inhibitory analysis and substrate specificity of studied extracellular enzymes indicate that they belong to a class of serine proteinases of subtilisin-like type.     

Effect of mild heat treatment on the ATPase activity and proteolytic sensitivity of myosin subfragment-1

The K+-EDTA-activated ATPase activity of chymotryptic myosin subfragment-1 (S-1) decreased by 85-90% when S-1 was incubated over a 2-h period at 35 degrees C. Addition of F-actin, ATP, or ATP analogs, such as ADP or PPi, to S-1 before incubation at 35 degrees C prevented the loss of ATPase activity. The decrease in ATPase activity was also accompanied by changes in tryptic sensitivity. Instead of the normal peptide pattern--which is comprised of three heavy chain fragments (27K, 50K, and 20K)--only two fragments (27K and 20K) appeared on the sodium dodecyl sulfate-gel electrophoregram after limited tryptic digestion of thermally treated S-1. Addition of any ligand--e.g. ATP, ADP, pyrophosphate, or actin--which prevented the loss of ATPase activity during incubation at 35 degrees C also prevented the observed change in the tryptic peptide pattern of S-1. Tryptic digested S-1, whose heavy chain has been cleaved to 27K, 50K, and 20K fragments, also lost its ATPase activity upon mild heat treatment. The heat-treated trypsin-digested S-1 was subjected to a second tryptic digestion, which resulted in the disappearance of the 50K fragment, while the 50K fragment of tryptic S-1 not subjected to heat treatment was not susceptible to additional tryptic hydrolysis. The results indicate that the structural changes, that take place specifically in the 50K region of S-1 upon mild heat treatment, lead to both the loss of the ATPase activity and the changed tryptic sensitivity of S-1.     

Effect of different nitrogen and carbon sources on the proteolytic activity

Two-three fold increases in the levels of proteolytic activities in one strain of Bacillus licheniformis (R1-8) were obtained when changes in the nature of the nitrogen source (food and fodder yeast instead of soybean meal) and in the amount of invert sugars in the culture medium were performed.     

Inventory of proteolytic activity of a new collagenolytic bacteria Empedobacter collagenolyticum

During the growth of Empedobacter collagenolyticum on a medium with gelatin, only one proteinase, a collagenase, was excreted in the culture medium. No other proteolytic activity was detected in the extracellular medium or in acellular extracts. The other proteases of this bacteria are principally intracellular peptidases. By electrophoresis of an acellular extract five peptidases were separated; they were aminopeptidases and dipeptidases. Some of them exhibited a specificity towards peptides with aminoacid frequently found in collagen; Gly-Leu, Gly-Pro, Pro-Gly-Gly. Two other peptidases seem to have special specificity, one of them hydrolyses peptides with lysine residues at the NH2 terminal end, the other one hydrolyses dipeptides of the structure Lys-X. These enzymes were also found in the culture medium; they certainly play an important role in bacterial nutrition.     

Effect of mutation on DNA-composition of some bacteria

The aim of this study was to investigate whether DNA from bacteria would be drastically changed by spontaneous and induced mutation. Melting points of pure DNA were taken as a criterion to indicate possible changes. DNA from dark-blue Chromobacteria and from some pale-blue and non-pigmented spontaneous variants had the same melting point, indicating only a very small overall change in its base composition. A similar situation held forAcetobacter aceti (liquefaciens) and an Mn-induced mutant. A wild-typeAgrobacterium tumefaciens B6 and its streptomycin-resistant mutant S1 behaved similarly. However, pure DNA from another, UV-induced, mutant M39 had a melting point which was 1.5 C higher, showing that considerable alterations in the structure of DNA may occur upon mutation. The results are discussed.