Gram-negative vibrio bacteria

The relatively heat-stable endotoxins are released by autolysis of the bacteria. Cholera toxins (Af, 84,000-102,000) are endotoxins released from the Gram-negative Vibrio cholerae in the intestine. They are composed of two functionally different subunits, L and H.The L subunit has a high affinity for ganglio-sides of the membranes of nerve cells, adipocytes, erythrocytes, etc., while the H subunit is responsible for toxicity. The colicins (Af, 60,000) are endotoxins produced by intestinal bacteria. Their toxicity is due to inhibition of cell division and inhibition of DNA and RNA degradation (colicin E2), or to inhibition of protein biosynthesis by inactivation of the 30S ribosomal subunit (colidn E3). 

AHLs are found only in Gram-negative bacteria, whereas AI-2 regulates phenotypes in genera as diverse as the firmicute B. subtilis and the y-proteobacterium V. harveyi. As a result, AI-2 has been proposed to be involved in interspecies communication (23). Homologues of LuxQ have only been found in Vibrio species. Therefore, it can be assumed that sensing of AI-2 occurs in a different way in other species. For example, in E. coli and Salmonella typhimurium, AI-2 is imported into... 

As reviewed by Rietschel Cavaillon (1-3), the term endotoxin was coined by Richard Pfeiffer, a student of Robert Koch. Pfeiffer first identified endotoxin as an agent responsible for fever and shock in animals that were injected with heat-killed preparations of Vibrio cholerae, or organisms that had been neutralized with antibodies (4). Until the end of his career, he was unaware that the O-antigens of gramnegative bacteria were covalently attached to the substance he had called endotoxin. It fell to Boivin, Staub, Luderitz, and others to demonstrate the lipopolysaccharide nature of endotoxin, to show that it was the principal glycolipid component of the outer membrane of gram-negative bacteria, and ultimately, to solve its chemical structure (5-8). 

Up to now, enzymatic isomerization has been evidenced mainly in Pseudomonas and Vibrio species. The fact that such an adaptation system was found in these organisms explains their wide occurrence in all niches of a great number of ecosystems, comprising soil, human skin, and water, also in comparison with other Gram-negative bacteria or species lacking such adaptation. 

In vitro, there has been observed the possible antimicrobial activity of oleuropein against human pathogenic bacteria. Moreover, the phenolic compound also confirmed its action on gram-positive and gram-negative bacterial strains such as Salmonella spp., Vibrio spp. and Staphylococcus aureus [91]. Experimental data indicated that M. pneumoniae, M hominis, M fermentans and M pirum are vulnerable to oleuropein [92]. 

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