H-NOX proteins in the virulence of pathogenic bacteria

Nitric oxide (NO) is a toxic gas encountered by bacteria as a product of their own metabolism or as a result of a host immune response. Non-toxic concentrations of NO have been shown to initiate changes in bacterial behaviors such as the transition between planktonic and biofilm-associated lifestyles. The heme nitric oxide/oxygen binding proteins (H-NOX) are a widespread family of bacterial heme-based NO sensors that regulate biofilm formation in response to NO. The presence of H-NOX in several human pathogens combined with the importance of planktonic–biofilm transitions to virulence suggests that H-NOX sensing may be an important virulence factor in these organisms. Here we review the recent data on H-NOX NO signaling pathways with an emphasis on H-NOX homologs from pathogens and commensal organisms. The current state of the field is somewhat ambiguous regarding the role of H-NOX in pathogenesis. However, it is clear that H-NOX regulates biofilm in response to environmental factors and may promote persistence in the environments that serve as reservoirs for these pathogens. Finally, the evidence that large subgroups of H-NOX proteins may sense environmental signals besides NO is discussed within the context of a phylogenetic analysis of this large and diverse family.     

The effect of copper concentration on the virulence of pathogenic Vibrio harveyi

AIM: To demonstrate the influence of copper on luminescence and toxin production in Vibrio harveyi. METHODS AND RESULTS: The effect of copper concentration on the expression of both luminescence and toxin of V. harveyi was investigated. Copper concentration of less than 40 ppm had no effect on the growth. While V. harveyi cultured with 40 ppm copper concentration showed decreased luminescence as measured by spectrofluorophotometer and as observed. LuxD gene, which is related to luminescence expression, was monitored using real-time RT-PCR. Result showed that the concentration of cDNA coding for luxD was lower in V. harveyi with copper. Toxic activity against both HeLa cells and shrimp haemocytes was also lower in the culture supernatant of V. harveyi grown with 40 ppm copper concentration. Moreover, V. harveyi extracellular proteins were analysed using SDS-PAGE. Results showed that culture supernatant from V. harveyi grown without copper had thicker band indicating a higher concentration of the putative cysteine protease, one of the major toxin of V. harveyi. CONCLUSIONS: This study proved that both luminescence and toxin were repressed by copper. SIGNIFICANCE AND IMPACT OF THE STUDY: The current study demonstrated that copper inhibited expression of phenotype of V. harveyi. Furthermore, it may inhibit quorum sensing of V. harveyi.     

The effect of Quercus castaneifolia extract on pathogenic enteric bacteria

The family of Enterobacteriaceae is a major group of gram negative bacteria, some of these microorganisms are pathogen and could cause disease mainly gastroenteritis. Recently, due to drug resistant nature of these bacteria specially in developing countries treatment of the patient considered as important investigate. Quercus castaneifolia is a native plant of Yasuj province in Iran, which the people who living in this area consume the fruit of this plant for treatment of enteric disease. Hence, the present study was conducted to evaluate the effect of fruit of Q. castaneifolia extract on pathogenic enteric bacteria viz., E. coli, Salmonella typhimurium, Shigella dysenteriae and Yersinia enterocolitica.Antimicrobial susceptibility and minimal inhibitory concentration (MIC) of the extracts were assessed by gel diffusion method and modification of E-test respectively. All the experiments were performed in triplicate and the statistical analysis was carried out on the results. The results obtained from this study indicated that alcoholic extract was shown antimicrobial effect on the microorganisms tested. In addition, S. dysentriae was more sensitive with zone of inhibition 18 mm and MIC value was 2.5 × 10⁻⁴ whereas, E. coli was less sensitive with zone of inhibition 12 mm and MIC value 1 × 10⁻². Salmonella typhimurium and Yersinia enterocolitica showed relatively intermediate susceptibility to the extract with zone of inhibition of 14 mm and MIC value 5 × 10⁻³. Overall, Q. castaneifolia may be considered for treatment of the patients suffering from enteric disease.     

Kin selection, quorum sensing and virulence in pathogenic bacteria

Bacterial growth and virulence often depends upon the cooperative release of extracellular factors excreted in response to quorum sensing (QS). We carried out an in vivo selection experiment in mice to examine how QS evolves in response to variation in relatedness (strain diversity), and the consequences for virulence. We started our experiment with two bacterial strains: a wild-type that both produces and responds to QS signal molecules, and a lasR (signal-blind) mutant that does not release extracellular factors in response to signal. We found that: (i) QS leads to greater growth within hosts; (ii) high relatedness favours the QS wild-type; and (iii) low relatedness favours the lasR mutant. Relatedness matters in our experiment because, at relatively low relatedness, the lasR mutant is able to exploit the extracellular factors produced by the cells that respond to QS, and hence increase in frequency. Furthermore, our results suggest that because a higher relatedness favours cooperative QS, and hence leads to higher growth, this will also lead to a higher virulence, giving a relationship between relatedness and virulence that is in the opposite direction to that usually predicted by virulence theory.     

Silkworm pathogenic bacteria infection model for identification of novel virulence genes

Silkworms are killed by injection of pathogenic bacteria, such as Staphylococcus aureus and Streptococcus pyogenes, into the haemolymph. Gene disruption mutants of S. aureus whose open reading frames were previously uncharacterized and that are conserved among bacteria were examined for their virulence in silkworms. Of these 100 genes, three genes named cvfA, cvfB, and cvfC were required for full virulence of S. aureus in silkworms. Haemolysin production was decreased in these mutants. The cvfA and cvfC mutants also had attenuated virulence in mice. S. pyogenes cvfA-disrupted mutants produced less exotoxin and had attenuated virulence in both silkworms and mice. These results indicate that the silkworm-infection model is useful for identifying bacterial virulence genes.     

The effect of low temperature on Streptococcus lactis

Summary When milk cultures of Streptococcus lactis are held near 0⁰, the number of living cells decreases rather slowly for about one month. Even after 3 months, viable cells are still present, though reduced to a few thousands. The death is partly due to accumulation of acid, but mainly to oxygen. Neutralization and replacement of the free oxygen by nitrogen in the culture prolong the viability.The early cessation of fermentation when large numbers of cells are kept in milk at 0⁰ (or at any temperature below the growth minimum) is due to some damaging effect of oxygen which the inactivated growth mechanism can not prevent or repair.The enzyme content of the cells, measured by their fermenting capacity (mg lactic acid per cell per hour) slowly decreases at temperatures below the growth minimum. After restoration of higher temperatures, the cells recover their enzyme content very slowly, and require several generations for complete recovery.The damage caused by oxygen is not the cause, but the result of the minimal temperature of growth.     

The effect of low temperature on the intensity of nitrification

Исследовали процесс нитрификации в образцах почвы, взятых с половины июля до половины ноября и инкубировавшихся при температуре, во-первых, 2°C во-вторых, 20°C. Образцы брали в дубовых и буковых лесах. Было установлено, что при такой низкой температуре, как +2°C, нитрификация достигает значительных величин. Другим интересным открытием является то, что б осенние месяцы, когда нитрификация при 20°C падает до весьма низких показателей, нитрификация при 2°C сохраняет значительную интенсивность, так что ее показатели часто равняются величиным нитрификации при 20°C. Как мы убедились, это положение обусловлено не тем, что инкубация при 2°C продолжается вдвое дольше, чем инкубация при 20°C. Главной причиной скорее являются, как кажется, понижение иненсивности аммонизации вследствие недостатка веществ, которые при разложении дают аммиак.     

The effect of slurry storage and anaerobic digestion on survival of pathogenic bacteria

The decline in viable numbers of Salmonella typhimurium, Yersinia enterocolitica and Listeria monocytogenes in beef cattle slurry is temperature-dependent; they decline more rapidly at 17°C than at 4°C. Mesophilic anaerobic digestion caused an initial rapid decline in the viable numbers of Escherichia coli, Salm. typhimurium, Y. enterocolitica and L. monocytogenes. This was followed by a period in which the viable numbers were not reduced by 90%. The T₉₀ values of E. coli, Salm. typhimurium and Y. enterocolitica ranged from 0.7 to 0.9 d during batch digestion and 1.1 to 2.5 d during semi-continuous digestion. Listeria monocytogenes had a significantly higher mean T₉₀ value during semi-continuous digestion (35.7 d) than batch digestion (12.3 d). Anaerobic digestion had little effect in reducing the viable numbers of Campylobacter jejuni.     

The effect of phospholipids on the adhesive properties of bacteria]

The present work shows that choline-containing phospholipids (lysophosphatidylcholine and lyso-1-alkyl-sn-glycerophosphocholine) inhibit the adhesion of some strains: Bacterium bifidum 1, B. adolescentis MC-42, B. longum B. 379M, Staphylococcus aureus P 209 and Klebsiella pneumoniae 52. Phosphatidylcholine produces no effect on the adhesiveness of these strains, while platelet activation factor stimulates adhesiveness only in strain S. aureus 209. The stimulating or inhibiting action of phospholipids on the adhesive process of microorganisms depends on the species of bacteria and on the concentration of reagents.     

The effect of incubation temperature on struvite formation by bacteria

The influence of incubation temperature on struvite precipitation by 54 bacterial strains isolated from soil and fresh water was investigated. Bacterial crystal formation was found at all temperatures assayed, the best results being obtained at 5 and 25°C. A steady reduction in precipitation was observed when the incubation temperature was increased above 30°C The results of the present study led us to think that temperature may in fact have a direct influence on the biological precipitation of struvite.     

病原真菌和细菌毒性基因的分离和鉴别

本文讨论最新发展起来的病原真菌和细菌毒性基因的分离和鉴别原理和方法,涉及到基因表达分析法、基因转移方法、基因组比较法、诱变方法及其诱变子的筛选鉴定。着重讨论了这些方法的优点和局限性,评估了标记诱变法（ＳＴＭ）和限制酶介导的整合法（ＲＥＭＩ）两者相互结合在病原真菌毒性基因克隆中的应用潜力。     

The multiplication dynamics of pathogenic bacteria in relation to the trophic and temperature cultivation conditions

The comparative study of the dynamics of multiplication of Listeria monocytogenes and Yersinia pseudotuberculosis in organic and synthetic media and in distilled water at temperatures of 37 degrees C and 6 degrees C was carried out. This study revealed that in organic media the multiplication of bacteria was good at 37 degrees C and 6 degrees C. In mineral media and distilled water their multiplication was observed only at 6 degrees C. Moreover, conditions necessary for the multiplication of pathogenic bacteria in distilled water were shown; these conditions depended on the inoculated dose, the number of autolyzed microbial cells and the state of the culture. Proofs of the multiplication of the bacteria under the conditions of minimum nutrition and low temperature were obtained with the use of labeled 3H-thymidine.     

Photodynamic effect of quinacrine on bacteria]

The acridine dye quinacrine (QA) was tested with regard to the photodynamic action on bacteria (Proteus mirabilis, Escherichia coli). The absorption maximum of the yellow dye QA ist in contrary to the photodynamically active dyes methylene blue (MB) and thiopyronine (TP) situated in the short wave region of the visible spectrum. Using for illumination a common light source--they have in general a weak emission in the short wave region--relatively high concentrations of QA are necessary for photodynamic action, and the difference between photodynamic inactivation and toxic effect is small. Using that light source XBO 500 with nearly equal emission in the range from 400 to 700 nm, a distinct photodynamic action of QA results. Comparing the photodynamic action of QA with those of MB and TP, QA has a low photodynamic effect, and the kinetics of inactivation of bacteria with QA is completely different from those obtained with the dyes MB and TP.