Microbios最新文献

Streptomyces nasri strain YG62 produces a broad-spectrum antibiotic designated actinomycin X2. The influence of static and shaken incubation on the production of actinomycin X2 and lipid profiles of S. nasri strain YG62 was investigated. It was found that shaken incubation was superior to the static process for both actinomycin X2 (2-fold) and total lipids (1.6-fold). Triglyceride and phospholipid levels paralleled the actinomycin X2 production with an increase in the triglyceride (2.8-fold) and phospholipid (1.2-fold) concentrations in the shaken culture over the static incubation. Analysis of fatty acid patterns revealed the occurrence of a wide range of fatty acids (C10-C22). The mean percentage of total saturated fatty acids in shaken culture was higher than those of the static culture. The mean percentage of mono-unsaturated fatty acids was almost the same in both cultures. The mean percentage of the total polyunsaturated fatty acids in the static culture was slightly higher than that of the shaken culture. The polyunsaturated/saturated fatty acid ratio (P/S) was higher in the static culture compared with the shaken culture. A positive correlation was recorded between triglycerides, phospholipids and actinomycin X2. A negative correlation on the other hand, was found between fatty acids and actinomycin X2.

Poultry feed contains a significant reservoir of bacteria and is a possible source of Salmonella typhimurium, Staphylococcus aureus and Escherichia coli, which can potentially infect farm animals and humans. The objective of this study was to determine whether the extract obtained from the culture of some Arthrinium species was able to inhibit the growth of these bacteria. The results obtained showed that the raw extracts of Arthrinium aureum, Arthrinium serenensis and Arthrinium phaeospermum inhibited the growth of Escherichia coli in poultry feed. In some cases the percentage inhibition of the growth of Escherichia coli was > 80%. With the raw extract of Arthrinium in poultry feed, the rate of growth of S. typhimurium fell to between 50% and 80%. The raw extract of A. serenensis had the lowest inhibitory activity. S. aureus counts were not affected by any Arthrinium raw extracts.

The nearly complete 16S rRNA gene sequences for oral Gram-negative anaerobic motile bacteria, Centipeda periodontii, Selenomonas sputigena and Selenomonas species (formerly S. sputigena type strain), were determined in order to unveil their relationship to other oral motile bacteria. To determine the phylogenetic characterization of these bacteria, their 16S rRNA gene sequences were obtained and compared with those from the ribosomal sequence databases previously reported. The 16S rRNA gene sequences of these bacteria were similar to those of Selenomonas ruminantium and Schwartzia succinivorans isolated from rumens, and to Pectinatus cerevisiiphilus isolated from spoiled beer. Among oral bacteria, the nucleotide sequence analysis of these bacteria revealed high nucleotide similarity to Veillonella species, whereas low similarity to oral motile bacteria such as Campylobacter species. Phylogenetic analysis clearly confirmed that C. periodontii and two Selenomonas species were classified as relatives of a group besides Selenomonas, Schwartzia, and Pectinatus species, and not as close relatives to oral motile bacteria, such as Campylobacter species. These results suggest that such oral Gram-negative anaerobic motile bacteria are close relatives of oral bacteria.

Pseudomonas aeruginosa, which was resistant to a wide variety of antibiotics, became sensitive to several of these antibiotics when grown and tested at 46 degrees C. Cell wall antibiotics such as penicillin G and ampicillin were only effective when added to cells growing at 46 degrees C prior to a temperature shift to 37 degrees C. Antibiotics which penetrate the cytoplasmic membrane to express their inhibiting action present a pattern different from those which are active against the outer cell wall. In order that these compounds be effective, the permeability of the cytoplasmic membrane must be further altered with agents such as EDTA which allow the penetration of actinomycin D. Inhibitors of protein synthesis, such as streptomycin and chloramphenicol, have increased access to their sites of action in cells grown at 46 degrees C. Cells grown at 46 degrees C have 40% less lipopolysaccharide (LPS) than cells grown at 37 degrees C and the LPS aggregates were of large molecular size in cells grown at 46 degrees C. Growth at 46 degrees C affects the permeability properties of the outer cell wall more than the permeability properties of the cytoplasmic membrane and this was due, in part, to the selective release of LPS of LPS-protein complexes at elevated growth temperatures.

The ability of strains of the Arthrinium genus to inhibit microbial development has been previously described. In the present work different periods of mutagenic treatment using ultraviolet light, and of nitrosoguanidine treatment, on strains of Arthrinium were investigated. With nitrosoguanidine treatment the survival rate ranged from 2.17 to 8.78%. Mutant strains were only obtained with a higher antibiotic production in comparison with the wild-strain, when the mutagenic agent was UV light.

Pseudomonas paucimobilis S37, a strain able to degrade 2,4,6-trichlorophenol (246-TCP), was isolated from an aquatic environment polluted with this compound. The effect of two natural organic compounds on the degradation of 246-TCP by this strain, in a no-growth state, was studied. Bacterial cultures were exposed to 0.1 mM and 0.5 mM of 246-TCP, alone, or in the presence of similar concentrations of glucose, a growth supporting substrate, or phenylalanine, a no-growth supporting compound. The effects on viable counts and 246-TCP degradation were measured. The bacterial culture died with 0.5 mM 246-TCP. This effect was overcome by the presence of glucose or phenylalanine, although no degradation of 246-TCP was detected. At 0.1 mM 246-TCP, the viability was not altered, and cells were able to degrade this compound. Glucose at 0.1 mM increased the degradative activity, but higher levels were inhibitory. Phenylalanine at 0.67 mM or higher concentration was also inhibitory of the 246-TCP degradation.

The effects of the lipopolysaccharides (LPS) of Proteus mirabilis (smooth and rough types), differing significantly in their composition on the release of compounds stored in specific platelet granules, were studied. There are two main types of secretory granules in blood platelets. Dense granules contain adenine nucleotides, and in alpha-granules different proteins are stored. The LPS were found to cause a dose-dependent release of proteins and adenine nucleotides. In the extracellular medium LDH activity was not present. The results presented in this study indicate that LPS from P. mirabilis act directly on blood platelets and induce the platelet secretory process. In comparison with thrombin, a strong platelet agonist, the action of the endotoxins tested was weak.

The immunomodulator properties of two species of halophilic Archaebacteria, Halobacterium saccharovorum and Halococcus rnorrhuae, were analysed by the study of lymphocyte activation. Two methods were used to detect activation in lymphocytes, namely incorporation of the radioactive nucleotide [3H]-thymidine, and CD25 expression. H. morrhuae had a stimulatory effect on human lymphocytes, but this action was observed only with the [3H]-thymidine uptake method, whereas H. saccharovorum produced no immunomodulator effect.

Metal incorporation and possible cellular compartmentalization of nickel by Staphylococcus aureus was investigated. Cells grown on nutrient agar were removed, washed and exposed to 10, 20, 50 or 100 ppm of nickel in distilled water. The cells were air-dried on Formvar coated grids and then examined in a transmission electron microscope operating in the scanning transmission mode. The spot setting was used in conjunction with an energy dispersive X-ray spectrometer to determine the location and relative amount of the nickel in different parts of the cells. The study showed that polyphosphate bodies bind large amounts of the metal. The peak height for nickel increased in the higher exposure amounts of nickel. No nickel was detected in the cell wall or cytoplasmic areas. The results are discussed in relation to nickel transport in cells and staphylococcal infections in humans.

Electron microscopy revealed that Streptococcus mitis ATCC 903 bound gold probes conjugated with goat IgG by non-immune mechanisms. Only a few of the cells and the cell wall fragments could bind IgG, in contrast to Staphylococcus aureus and Streptococcus group G which showed a more homogeneous binding to nearly all cells or cell wall fragments.