Bacterial pathogenicity is a result of a combination of factors, including resistance to environmental threats and to the host's defenses, growth capability, localization in the host, tissue specificity, resource obtaining mechanisms and the bacterium's own defenses to aggression. A variety of bacterial components, often specific to each strain, are involved in the microorganism's survival, adhesion and growth in the host. Many of them are harmful and, therefore, are called virulence factors. The effects caused by the virulence factors determine the degree of aggressivity of the strain. In many cases the virulence factors are secreted proteins or enzymes, sometimes performing very specific functions. The enzymatic activity is directed to specific proteins from cell membranes, synaptic vesicle fusion proteins, among other important targets. One of the most toxic bacterial proteins is secreted by Clostridium botulinum, targeted to synaptic vesicle fusion proteins, cleaving them with a zinc-metalloprotease activity, which results in severe neurotoxic effects with a lethal dose as low as eight nanograms per kilogram of body weight. The tetanus neurotoxin acts in a similar way but is less active and Bacillus anthracis also presents a potent metalloprotease activity. In this work we describe a selection of these specially interesting and important bacterial proteins and proteases, stressing their relevance in the pathological process and in medical studies.
Peptides that display bradykinin-potentiating activity have been obtained from a number of distinct sources, such as snake venoms, fibrinogen, and casein. This paper describes the characterization of two new peptides generated by tryptic hydrolysis of casein. No homology was found with other known vasoactive or vasopotentiating peptides, especially by the lack of Ile-Pro-Pro motif. The peptides EMPFPK and YPVEPFTE, corresponding to the gamma casein sequence (108-113 and 114-121, respectively), displayed a selective potentiating activity on isolated guinea pig ileum for bradykinin. Besides, the octapeptide YPVEPFTE showed an in vitro competitive inhibitor effect on angiotensin-converting enzyme and thimet oligopeptidase and presented an opiate-like activity, increasing two times the latence time in the hot-plate assay. The results suggest that the isolated bioactive peptides act on conversion and/or inactivation of endogenous peptides by enzymes such as angiotensin-converting enzyme and thimet oligopeptidase by modifying several systemic responses such as blood-pressure regulation and in pain response.
Copper mining has polluted soils and water, causing a reduction of the microbial diversity and a change in the structure of the resident bacterial communities. In this work, selective isolation combined with MALDI-TOF MS and the 16S rDNA method were used for characterizing cultivable bacterial communities from copper mining samples. The results revealed that MALDI-TOF MS analysis can be considered a reliable and fast tool for identifying copper-resistant bacteria from environmental samples at the genera level. Even though some results were ambiguous, accuracy can be improved by enhancing reference databases. Therefore, mass spectra analysis provides a reliable method to facilitate monitoring of the microbiota from copper-polluted sites. The understanding of the microbial community diversity in copper-contaminated sites can be helpful to understand the impact of the metal on the microbiome and to design bioremediation processes.
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