Essay On Microbiota

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Introduction

To understand the human gut health and aetiology, the first step is to understand the gastrointestinal (GI) microflora and its distribution through the digestive system [2]. The human GI tract is inhabited by trillions of microorganisms, which together is known as the microbiota [5]. These microorganisms come from both archeal and bacterial domains. Bacteria are the predominant kingdom of organisms and it is composed mainly by five bacterial phyla: Firmicutes, Bacteroidetes, Actinobacteria, Proteobacteria and Verrucomicrobia [3]. The great majority of mammalian gut microbiota belongs to the three phyla: the Gram-negative anaerobe Bacteroidetes, the Gram-positive Actinobacteria and Firmicutes [5].
Firmicutes comprises of over 200 genera, including Lactobacillus, Clostridium, Bacillus, and Mycoplasma [5]. The gram-negative Bacteroidetes includes Bacteroides, Prevotella and Xylanibacter, that can degrade a variety of complex glycans [3]. The composition of the microbiota is different in each individual, even if there is a core gut microbiota that is shared among individuals; this is due to different life circumstances such as the food eaten throughout life, the medicine intake, and the geographic situations of the individual etc. [3].

When still inside the uterus a fetus has a sterile GI tract. Certain microbes colonize particular intestinal habitats at various times after the birth, this is characteristic of that particular habitat and animal host [10]. The contamination by the heterogeneous collection of microbes occurs under the birth. After a few days the colonizing of the GI tract is mainly represented by lactic acid bacteria and coliforms. It is during the weaning that the composition is distinctly altered, and...

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The specific protein export pathways and the general secretory pathway (GSP) are the two central forms of secretion pathways. GSP is an ATP dependent system, where the proteins are synthesized as preproteins, with the presence of a signal peptide in the N-terminal part of the amino acid sequence [26].

Nuclease is one of the acknowledged proteins secreted by members of the genus Lactobacillus. After several evidences of extracellular DNAse activity, nucleases from several Lactobacillus species have been identified by two methods; sodium dodecyl sulfate polyacrylamide gel electrophoresis, coupled to in-gel protein renaturalization and nuclease assay [28]. It has been shown that nuclease activity over the DNA present in the luminal content, can lead to the formation of a set of diverse oligonucleotides, some of them with immunomodulatory properties [29, 30, 31].

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