Author(s): Zehara Mohammed Damtew

Abstract: Prokaryotes were originally defined as single celled entities by their cellular structure, such as the lack of a nucleus, division by fission, special structure of the cell wall. Prokaryotes are found nearly everywhere in the modern world and their presence defines the biosphere. They are also phylogenetic ally the most diverse; as two out of the currently recognized three major divisions domains of living organisms Bacteria, Archaea and Eucarya consist of prokaryotes. Prokaryotes are subdivided into 30 phyla in the domain Bacteria and five phyla in the domain Archaea. Most described prokaryotic species belong to only four of the 30 bacterial phyla, whereas the majority of phyla are hardly represented by living isolates. The absence of living isolates to calibrate overall bacterial diversity resulted in pragmatic challenges to taxonomically characterize the bacterial diversity known only from culture independent methods. Thus, searching as an alternative that could eventually lead to a more realistic understanding of prokaryotic biodiversity, provide biotechnology with new tools and maybe even contribute to develop a model of prokaryotic evolution. Many bacteria are known to regulate their cooperative activities and physiological processes through a mechanism called quorum sensing (QS), which bacterial cells communicate with each other by releasing, sensing and responding to small diffusible signal molecules. The ability of bacteria to communicate and behave as a group for social interactions. That provided benefits to bacteria in host colonization, formation of biofilms, defense against competitors and adaptation to changing environments.

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