Folia Microbiologica

A new Type II restriction endonucleaseApaCI purified fromAcetobacter pasteurianus is an isoschizomer ofBamHI that cleaves at the nucleotide sequence 5′-G/GATCC-3′ of double-stranded DNA. The single restriction activity present in this strain permits rapidly purified 30 000 units of cleavage activity from 10 g of freshly harvested cells. The resultingApaCI preparation is free of contaminant nuclease activities that might interfere within vitro manipulation of DNA.

The composition of fatty acids in lipids of selected strains of non-pathogenic unidentified corynebacteria was determined with the aim to employ such determinations for their characterization. Four strains were characterized by the presence of branched iso- and anteisoacids. One strain corresponded according to its composition to mycobacteria and nocardiae.

The bactericidal activity of sera obtained from piglets reared without maternal colostrum and under sterile conditions, was studied. These sera, which contain complement, but not even a trace of antibody, do not have a bactericidal effect on strains ofEscherichia coli andSalmonella in the S phase. The sera of sterile piglets artificially colonized with a given type ofEscherichia coli showed a bactericidal effect within 4—7days after administration of the bacteria. This effect was specific for the strains with which the piglets had been colonized. Bacteria of a different antigenic character were susceptible to the action of the serum of these animals only after adding a small amount of the corresponding specific antibody. Quantitative experiments showed that the bactericidal test was extremely sensitive for determining antibodies which could be detected in concentration by three to four orders lower than by the agglutination test. Strains not possessing a complete set of antigens (in the R phase) were susceptible no the action of the serum of newborn animals containing only complement and no antibodies. The results show that complement acts directly on the R phase of bacteria. The view that the properdin system is identical with the bactericidal function of antibody and complement has been discussed and seems supported by these data.

The ability was determined of the rumen ciliate Eudiplodinium maggii to utilize chitin from fungal cell wall. Cultivation experiments shoved that the population concentration (number of ciliates in vitro) was positively correlated with chitin doses. Cell extract prepared from the bacteria-free ciliates degraded colloidal chitin releasing 2.0 μmol reducing sugar per mg protein per h. End products of this reaction were chitotriose and N-acetylglucosamine. Incubation of the bacteria-free ciliates with chitin resulted in an increase in the concentration of acetic, propionic and butyric acids in the incubation medium. The production rate of total volatile fatty acids (VFA) by ciliates incubated with and without chitin was 45.0 and 30.5 pmol VFA per protozoan, respectively, the molar proportion of particular acids remaining unchanged.

The presence of virulence factors in 96Aeromonas strains isolated from food and clinical samples was studied. Neither cytotoxic activity and hydrophobicity, not the presence of pili or an extra surface layer made it possible to establish differences between food and clinical strains. Statistical studies showed that cytotoxin production was associated with a positive Voges—Proskauer reaction, inability to ferment arabinose and a positive lysine decarboxylation. Therefore, when comparing cytotoxic clinical and food strains with lysine decarboxylation phenotype, there was a significant difference (p<0.05) between the two groups. The association of a cytotoxin production and lysine decarboxylation character should thus be considered as a possible virulence marker.

Streptococcus dysgalactiae subsp. equisimilis (SDSE), belonging to the group C and G streptococci, are human pathogens reported to cause clinical manifestations similar to infections caused by Streptococcus pyogenes. To scrutinize the distribution of gene coding for S. pyogenes virulence factors in SDSE, 255 isolates were collected from humans infected with SDSE in Vellore, a region in southern India, with high incidence of SDSE infections. Initial evaluation indicated SDSE isolates comprising of 82.35% group G and 17.64% group C. A multiplex PCR system was used to detect 21 gene encoding virulence-associated factors of S. pyogenes, like superantigens, DNases, proteinases, and other immune modulatory toxins. As validated by DNA sequencing of the PCR products, sequences homologous to speC, speG, speH, speI, speL, ssa and smeZ of the family of superantigen coding genes and for DNases like sdaD and sdc were detected in the SDSE collection. Furthermore, there was high abundance (48.12% in group G and 86.6% in group C SDSE) of scpA, the gene coding for C5a peptidase in these isolates. Higher abundance of S. pyogenes virulence factor genes was observed in SDSE of Lancefield group C as compared to group G, even though the incidence rates in former were lower. This study not only substantiates detection of S. pyogenes virulence factor genes in whole genome sequenced SDSE but also makes significant contribution towards the understanding of SDSE and its increasing virulence potential.

Мы исследовали динам ику количества клето к актиномицетов в прик орневых зонах пшениц ы, ячменя и овса в течени е периода их вегетаци и. У изолированных актин омицетов мы определя ли их противогрибковые свойства. Актиномице ты находились во внешне й ризосфере ячменя, пшеницы и овса в течен ие всех исследовавши хся фаз роста растений. Их кол ичество сильно колебалось. Мы считае м весьма многообещаю щим, — с точки арения использовани я в фитопатологии антагонистических с войств актиномицето в, — присутствие большого количества актиномицетов в зоне корней молодых расте ний, у которых опасность по ражения паразитичес кими грибками особенно ве лика. Размещение акти номицетов с противогрибковыми с войствами весьма напоминало ра змещение почвенных г рибков. Не наблюдалось сколько-нибудь выразительной разни цы между антагониста ми из почвы, прилегающей к корням злаков, и антагониста ми в контрольной незасе янной почве. 22% из 127 изоли рованных нами штаммов подавля ло при испытаниях рост м икроорганизмов Fusarium nivale, Fusarium oxysporum и Alternaria solani.

In the current study, eight strains of bifidobacteria and seven strains of lactobacilli were tested for their ability to grow in the presence of rebaudioside A and steviol glycosides from the sweetener Natusweet M001 originating from herb Stevia rebaudiana (Bertoni). Stevia is gaining popularity as a natural, non-caloric sugar substitute, and recently, it was allowed as a food additive by European Union too. Utilisation of steviol glycosides by intestinal microbiota suggests that they might have potential prebiotic effect. Based on the evaluation of bacterial density and pH values in our in vitro study, it was found that lactobacilli and bifidobacteria tested were able to utilise steviol glycosides as a carbon source only to a very limited extent. All strains tested showed significantly lower change in the absorbance A540 (P < 0.05) and pH decrease of the growth media as compared with the positive controls (medium containing glucose as a carbon source and de Man Rogosa Sharpe broth). We concluded that a suggested prebiotic effect was not confirmed either in the case of rebaudioside A or in the case of the sweetener Natusweet M001 containing a mixture of steviol glycosides.

The distribution of bromophenol blue between the cell and the medium was used to calculate the intracellular pH of yeast. In buffered media the intracellular pH exhibited a plateau at pH i =5.8 for low external pH values and another at pH i =7.6 for high external pH values. The production of H ions by the yeast during utilization of glucose is not accompanied by an alkalinization of the cell interior. The pH i even decreases somewhat in the presence of glucose and K ions.