Home About us Contact
|
Home About us Contact | ||
|
|
||
Bacterial Processes (bacterial + process)
Selected AbstractsInteraction of live and dead Escherichia coli O157:H7 and fluorescent microspheres with lettuce tissue suggests bacterial processes do not mediate adherenceLETTERS IN APPLIED MICROBIOLOGY, Issue 2 2006E.B. Solomon Abstract Aims:, The goal of this study was to determine whether any specific bacterial processes (biochemical or genetic) or cell surface moieties were required for the interaction between Escherichia coli O157:H7 and lettuce plant tissue. Methods and Results:,Escherichia coli O157:H7 and FluospheresTM (fluorescent polystyrene microspheres) were used in experiments to investigate interactions with lettuce. FluospheresTM were used as they are a nonbiological material, of similar size and shape to a bacterial cell, but lack bacterial cell surface moieties and the ability to respond genetically. Live and glutaraldehyde-killed E. coli O157:H7 attached at levels of c. 5·8 log10 cells per cm2 following immersion of lettuce pieces into a suspension containing c. 8 log10 CFU ml,1. In a separate experiment, numbers of bacteria or FluospheresTM associated with lettuce decreased by c. 1·5 log cm,2 following a 1-min wash. Exposure times of 1 min, 1 h, or 6 h had little effect on the level of attachment for FluospheresTM, and live or killed cells of E. coli O157:H7 to lettuce tissue. Significance:, These results indicate that bacterial processes and cell surface moieties are not required for the initial interaction of E. coli O157:H7 to lettuce plant tissue. [source] Insights into the function of the WhiB-like protein of mycobacteriophage TM4 , a transcriptional inhibitor of WhiB2MOLECULAR MICROBIOLOGY, Issue 3 2010Jan Rybniker Summary WhiB-like proteins of actinomycetes are known to co-ordinate iron-sulfur (Fe-S) clusters and are believed to have regulatory functions in many essential bacterial processes. The systematic determination of the genome sequences of mycobacteriophages has revealed the presence of several whiB -like genes in these viruses. Here we focussed on the WhiB-like protein of mycobacteriophage TM4, WhiBTM4. We provide evidence that this viral protein is capable of co-ordinating a Fe-S cluster. The UV-visible absorption spectra obtained from freshly purified and reconstituted WhiBTM4 were consistent with the presence of an oxygen sensitive [2Fe-2S] cluster. Expression of WhiBTM4 in the mycobacterial host led to hindered septation resembling a WhiB2 knockout phenotype whereas basal expression of WhiBTM4 led to superinfection exclusion. The quantification of mRNA-levels during phage infection showed that whiBTM4 is a highly transcribed early phage gene and a dominant negative regulator of WhiB2. Strikingly, both apo-WhiB2 of Mycobacterium tuberculosis and apo-WhiBTM4 were capable of binding to the conserved promoter region upstream of the whiB2 gene indicating that WhiB2 regulates its own synthesis which is inhibited in the presence of WhiBTM4. Thus, we provide substantial evidence supporting the hypothesis of viral and bacterial WhiB proteins being important Fe-S containing transcriptional regulators with DNA-binding capability. [source] Interdependence of two NarK domains in a fused nitrate/nitrite transporterMOLECULAR MICROBIOLOGY, Issue 3 2008Alan D. Goddard Summary Nitrate uptake is essential for various bacterial processes and combines with nitrite export to form the usual initial steps of denitrification, a process that reduces nitrate to dinitrogen gas. Although many bacterial species contain NarK-like transporters that are proposed to function as either nitrate/proton symporters or nitrate/nitrite antiporters based on sequence homology, these transporters remain, in general, poorly characterized. Several bacteria appear to contain a transporter that is a fusion of two NarK-like proteins, although the significance of this arrangement remains elusive. We demonstrate that NarK from Paracoccus denitrificans is expressed as a fusion of two NarK-like transporters. NarK1 and NarK2 are separately capable of supporting anaerobic denitrifying growth but with growth defects that are partially mitigated by coexpression of the two domains. NarK1 appears to be a nitrate/proton symporter with high affinity for nitrate and NarK2 a nitrate/nitrite antiporter with lower affinity for nitrate. Each transporter requires two conserved arginine residues for activity. A transporter consisting of inactivated NarK1 fused to active NarK2 has a dramatically increased affinity for nitrate compared with NarK2 alone, implying a functional interaction between the two domains. A potential model for nitrate and nitrite transport in P. denitrificans is proposed. [source] | ||||||||||