Bacteria

About: Bacteria is a research topic. Over the lifetime, 23676 publications have been published within this topic receiving 715990 citations. The topic is also known as: eubacteria.

The Detection of Chemical Mutagens with Enteric Bacteria

Abstract: Mutagens alter DNA. As the DNA of all organisms has the same double helical structure and the same four nucleotides, any organism may be used as an indicator system for mutagens. Bacteria have numerous advantages for the detection of mutagens, and we discuss these and describe various methods and strains. We also discuss the validity of the bacterial tests and their pertinence to human mutagenesis and carcinogenesis.

Berry phenolics selectively inhibit the growth of intestinal pathogens.

Abstract: R. PUUPPONEN-PIMIA¨ , L. NOHYNEK, S. HARTMANN-SCHMIDLIN, M. KAHKONEN, M. HEINONEN, K. MAATTA¨ -RIIHINEN AND K.-M. OKSMAN-CALDENTEY. 2005. Aims: To investigate the effects of berries and berry phenolics on pathogenic intestinal bacteria and to identify single phenolic compounds being responsible for antimicrobial activity. Methods and Results: Antimicrobial activity of eight Nordic berries and their phenolic extracts and purified phenolic fractions were measured against eight selected human pathogens. Pathogenic bacterial strains, both Gram- positive and Gram-negative, were selectively inhibited by bioactive berry compounds. Cloudberry and raspberry were the best inhibitors, and Staphylococcus and Salmonella the most sensitive bacteria. Phenolic compounds, especially ellagitannins, were strong inhibitory compounds against Staphylococcus bacteria. Salmonella bacteria were only partly inhibited by the berry phenolics, and most of the inhibition seemed to originate from other compounds, such as organic acids. Listeria strains were not affected by berry compounds, with the exception of cranberry. Phenolic compounds affect the bacteria in different mechanisms. Conclusions: Berries and their phenolics selectively inhibit the growth of human pathogenic bacteria. Significance and Impact of the Study: Antimicrobial properties of berries could be utilized in functional foods. Furthermore these compounds would be of high interest for further evaluation of their properties as natural antimicrobial agents for food and pharmaceutical industry.

Redox-Active Antibiotics Control Gene Expression and Community Behavior in Divergent Bacteria

Abstract: It is thought that bacteria excrete redox-active pigments as antibiotics to inhibit competitors. In Pseudomonas aeruginosa, the endogenous antibiotic pyocyanin activates SoxR, a transcription factor conserved in Proteo- and Actinobacteria. In Escherichia coli, SoxR regulates the superoxide stress response. Bioinformatic analysis coupled with gene expression studies in P. aeruginosa and Streptomyces coelicolor revealed that the majority of SoxR regulons in bacteria lack the genes required for stress responses, despite the fact that many of these organisms still produce redox-active small molecules, which indicates that redox-active pigments play a role independent of oxidative stress. These compounds had profound effects on the structural organization of colony biofilms in both P. aeruginosa and S. coelicolor, which shows that "secondary metabolites" play important conserved roles in gene expression and development.