Bacteria and Archaea
Bacteria and archaea are prokaryotes. They are single-celled with no nucleus. They used to be classified together, but they are now classified according to genetic material sequences biochemical and structural differences. Archaea are single-celled microorganisms with no nuclei (Long et al., 2019). They were initially classified as bacteria. Additionally, they were classified based on cell wall structures, substances they consume, and shapes. However, a proposal was made to classify different prokaryotes based on gene sequences. Archaea were thus classified separately from bacteria due to their ribosomal RNA. The evidence that led to archaea being classified separately was the lack of peptidoglycan in their cell walls, 16S rRNA, and two unusual coenzymes ((Long et al., 2019). Consequently, this led to the classification of organisms into three domains: eukaryotes, bacteria, and archaea.
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The classification of archaea is a contentious field. The current classification systems organize archaea into groups with similar structural features and common ancestry. Subsequently, modern classification relies on utilizing sequences of rRNA genes to prove relationships among organisms. This system is known as molecular phylogenetics, which evaluates hereditary molecular and genetic differences in DNA sequences to understand the evolutionary relationships of microorganisms (Richardson, 2019).
Archaea that reside in the human gut are mostly always methanogens. Studies in mice have revealed that methanogens contribute to human obesity (Nkamga et al., 2017). Another connection between methanogens and human health is chronic constipation. Methane slows down gut transit time, which may substantially contribute to constipation (Nkamga et al., 2017). Studies have revealed a lower prevalence of methanogens in patients with diarrhea than in healthy individuals (Nkamga et al., 2017). This shows that methanogens have a role in reducing intestinal transit time and, thus, constipation.
References
Long, X., Xue, H., & Wong, J. T. (2019). Descent of bacteria and Eukarya from an archaeal root of life. Evolutionary Bioinformatics. https://doi.org/10.1101/745372
Nkamga, V. D., Henrissat, B., & Drancourt, M. (2017). Archaea: Essential inhabitants of the human digestive microbiota. Human Microbiome Journal, 3, 1-8. https://doi.org/10.1016/j.humic.2016.11.005
Richardson, B. J. (2019). Evolutionary biogeography of Australian jumping spider genera (Araneae: Salticidae). Australian Journal of Zoology, 67(3), 162. https://doi.org/10.1071/zo20023
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Question
Discussion 2.1: Bacteria and Archaea
Define Bacteria and archaea.
These two terms used to be classified together.
Discuss what discoveries led to the separation of these two groups.
Identify the technique(s) used to reclassify these organisms.
Discuss whether or not archaea has a role in human health and disease.