Cytokine responses of bovine macrophages to diverse clinical Mycobacterium avium subspecies paratuberculosis strains.
(9/2638)
BACKGROUND: Mycobacterium avium subsp. paratuberculosis (MAP), the causative agent of Johne's disease (JD) persistently infects and survives within the host macrophages. While it is established that substantial genotypic variation exists among MAP, evidence for the correlates that associate specific MAP genotypes with clinical or sub-clinical disease phenotypes is presently unknown. Thus we studied strain differences in intracellular MAP survival and host responses in a bovine monocyte derived macrophage (MDM) system. RESULTS: Intracellular survival studies showed that a bovine MAP isolate (B1018) and a human MAP isolate (Hu6) persisted in relatively higher numbers when compared with a sheep MAP isolate (S7565) at 24-hr, 48-hr and 96-hr post infection (PI). MDMs stimulated with B1018 up-regulated IL-10 at the transcript level and down-regulated TNFalpha at the protein and transcript levels compared with stimulations by the S7565 and Hu6. MDMs infected with Hu6 showed a down regulatory pattern of IL-10 and TNFalpha compared to stimulations by S7565. Cells stimulated with B1018 and Hu6 had low levels of matrix metalloprotease-3 (MMP3) and high levels of tissue inhibitor of metalloprotease-1 (TIMP1) at 96-hr PI relative to MDMs stimulated by S7565. CONCLUSION: Taken together, results suggest that the bovine (B1018) and the human (Hu6) MAP isolates lead to anti-inflammatory and anti-invasive pathways in the macrophage environment whereas the sheep (S7565) MAP isolate induces a pro-inflammatory pathway. Thus the infecting strain genotype may play a role in polarizing the host immune responses and dictate the clinicopathological outcomes in this economically important disease. (+info)
Regulation of expression of atypical orphan response regulators of Helicobacter pylori.
(10/2638)
The human gastric pathogen Helicobacter pylori exhibits a remarkably small repertoire of transcriptional regulators including three complete two-component systems as well as the orphan response regulators HP1021 and HP1043. Both HP1021 and HP1043 show atypical receiver sequences and are required for the normal cell growth of H. pylori. Recently, we demonstrated that phosphorylation of HP1021 and HP1043 according to the two-component paradigm is not a prerequisite for the cell growth-associated functions of these response regulators, raising the question of how the activity of this regulatory proteins is modulated. Here, we report that strict transcriptional control of its expression is not involved in the cell-growth associated function of HP1021. We show that expression of hp1043 is controlled both on the post-transcriptional or post-translational level and by transcriptional regulation. Furthermore, we provide evidence that hp1043 can be replaced by the orthologous gene cj0355 from Campylobacter jejuni. (+info)
Effect of special Hungarian probiotic kefir on faecal microflora.
(11/2638)
AIM: To investigate the effect of a four-week consumption of a special Hungarian probiotic agent (Biofir) on the faecal microflora in human healthy subjects. METHODS: The effect of Biofir with 10(6)/cm3 initial germs on the faecal microflora was studied in 120 healthy volunteers (71 females, 49 males). The traditional Russian type kefir was used as control. The various germ groups and pH values were determined in wk 2, 4 and 6. RESULTS: The number of all microbes increased during the 4-week probiotic treatment. The number of microbes increased 4.3-fold in the control group and 6.8-fold in Biofir-treated group. The probiotic kefir caused multiplication of the probiotic flora, meanwhile the undesired bacteria multiplied in the control group. No significant change of pH values of the faeces was found in both groups. CONCLUSION: The Hungarian probiotic kefir (Biofir) is capable of promoting multiplication of probiotic bacterial flora in the large bowel. (+info)
Acanthamoeba castellanii promotion of in vitro survival and transmission of coxsackie b3 viruses.
(12/2638)
This work was undertaken to determine whether Acanthamoeba could play a role in the survival and transmission of coxsackieviruses and focused on in vitro interactions between Acanthamoeba castellanii and coxsackie B3 viruses (CVB-3). Residual virus titer evaluations and immunofluorescence experiments revealed a remarkable CVB-3 adsorption on amoeba surfaces and accumulation inside cells. The survival of viruses was independent of the dynamics of amoeba replication and encystment. In addition, our results indicated that virus-infected amoebas can release infectious viruses during interaction with human macrophages. On the basis of these data, Acanthamoeba appears to be a potential promoter of the survival of coxsackieviruses and their transmission to human hosts. (+info)
Investigation of the physiological relationship between the cyanide-insensitive oxidase and cyanide production in Pseudomonas aeruginosa.
(13/2638)
Pseudomonas aeruginosa is an opportunistic pathogen which demonstrates considerable respiratory versatility, possessing up to five terminal oxidases. One oxidase, the cyanide-insensitive oxidase (CIO), has been previously shown to be resistant to the potent respiratory inhibitor cyanide, a toxin that is synthesized by this bacterium. This study investigated the physiological relationship between hydrogen cyanide production and the CIO. It was found that cyanide is produced in P. aeruginosa at similar levels irrespective of its complement of CIO, indicating that the CIO is not an obligatory electron sink for cyanide synthesis. However, MICs for cyanide and growth in its presence demonstrated that the CIO provides P. aeruginosa with protection against the effects of exogenous cyanide. Nevertheless, the presence of cyanide did not affect the viability of cio mutant strains compared to the wild-type during prolonged incubation in stationary phase. The detection of the fermentation end products acetate and succinate in stationary-phase culture supernatants suggests that P. aeruginosa, irrespective of its CIO complement, may in part rely upon fermentation for energy generation in stationary phase. Furthermore, the decrease in cyanide levels during incubation in sealed flasks suggested that active breakdown of HCN by the culture was taking place. To investigate the possibility that the CIO may play a role in pathogenicity, wild-type and cio mutant strains were tested in the paralytic killing model of Caenorhabditis elegans, a model in which cyanide is the principal toxic agent leading to nematode death. The CIO mutant had delayed killing kinetics, demonstrating that the CIO is required for full pathogenicity of P. aeruginosa in this animal model. (+info)
The nonredundant roles of two 4'-phosphopantetheinyl transferases in vital processes of Mycobacteria.
(14/2638)
Mycobacterium tuberculosis contains >20 enzymes that require activation by transfer of the 4'-phosphopantetheine moiety of CoA onto a conserved serine residue, a posttranslational modification catalyzed by 4'-phosphopantetheinyl transferases (PPTases). The modified proteins are involved in key metabolic processes such as cell envelope biogenesis and the production of virulence factors. We show that two PPTases conserved in all Mycobacterium spp. and in related genera activate two different subsets of proteins and are not functionally redundant. One enzyme, AcpS, activates the two fatty acid synthase systems of mycobacteria, whereas the other PPTase, PptT, acts on type-I polyketide synthases and nonribosomal peptide synthases, both of which are involved in the biosynthesis of virulence factors. We demonstrate that both PPTases are essential for Mycobacterium smegmatis viability and that PptT is required for the survival of Mycobacterium bovis bacillus Calmette-Guerin. These enzymes are thus central to the biology of mycobacteria and for mycobacterial pathogenesis and represent promising targets for new antituberculosis drugs. (+info)
Delivery of nitric oxide released from beta-Gal-NONOate activation by beta-galactosidase and its activity against Escherichia coli.
(15/2638)
Beta-galactosyl-pyrrolidinyl diazeniumdiolates (beta-Gal-NONOate) is a new site-specific nitric oxide (NO)-releasing compound, which releases NO once activated by beta-galactosidase. In the present experiment, we used beta-Gal-NONOate as a bactericidal reagent to investigate its effectiveness of NO releasing. Through the evaluation of intracellular NO level and the comparison of survival of E. coli transformed with lacZ gene but treated with beta-Gal-NONOate and NONOate, respectively, it's evident that beta-Gal-NONOate had a higher bactericidal activity than conventional NONOate. While either beta-Gal-NONOate- or NONOate-treated E. coli without transferred lacZ gene showed low bactericidal activity. The results revealed that beta-Gal-NONOate was a potentially efficient NO donor, which took on a novel and promising approach to deliver NO into cells. (+info)
Viruses' life history: towards a mechanistic basis of a trade-off between survival and reproduction among phages.
(16/2638)
Life history theory accounts for variations in many traits involved in the reproduction and survival of living organisms, by determining the constraints leading to trade-offs among these different traits. The main life history traits of phages-viruses that infect bacteria-are the multiplication rate in the host, the survivorship of virions in the external environment, and their mode of transmission. By comparing life history traits of 16 phages infecting the bacteria Escherichia coli, we show that their mortality rate is constant with time and positively [corrected] correlated to their multiplication rate in the bacterial host. Even though these viruses do not age, this result is in line with the trade-off between survival and reproduction previously observed in numerous aging organisms. Furthermore, a multiple regression shows that the combined effects of two physical parameters, namely, the capsid thickness and the density of the packaged genome, account for 82% of the variation in the mortality rate. The correlations between life history traits and physical characteristics of virions may provide a mechanistic explanation of this trade-off. The fact that this trade-off is present in this very simple biological situation suggests that it might be a fundamental property of evolving entities produced under constraints. Moreover, such a positive correlation between mortality and multiplication reveals an underexplored trade-off in host-parasite interactions. (+info)