Types of Microorganisms

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Earth is surrounded by organisms which have independent roles to maintain various life processes. Microorganisms can be defined as living things that are invisible to our naked eyes and found abundantly in our environments. On the basis of ribosomal RNA (ribonucleic acid) sequencing, microorganisms are divided into three phylogenetically distinct domains, which has included the Archaea, the Bacteria and the Eukarya (Madigan, Martinko, Stahl, & Clark, 2012) (refer to Figure 1 in Appendix 1).
Archaea is the first domain of microorganisms. Archaeas are unicellular prokaryotes which vary from bacteria and eukaryotes (Pack, 2007). Pack (2007) stated that the cell walls of Archaeas consist of polysaccharides while the plasma membranes are made up of phospholipids. According to Cohen (2011), archaeal cell walls do not have peptidoglycan, cellulose or chitin. There are four main differences between archaeal membrane and other cells (Cohen, 2011). For instance, the hydrophobic chains of phospholipids are highly branched and ether-linked to glycerol (Pack, 2007). Archaeas have irregular shapes such as spheres, rods, or spirals (Levy, 2011) and some are triangular or square-shaped (Soloman, Berg & Martin, 2011). Besides that, Archaeas reproduce asexually through binary fission but not mitosis because the nucleus is absent (Hogan, 2011). Bej, Aislabie, and Atlas (2010) stated that the two main phyla of Archaeas are Crenarchaeota and Euryarchaeota.
According to Kratz (2005), most of the Crenarchaeota are hyperthermophiles that grow at temperature above 80oC. Kratz (2005) also mentioned that hyperthermophiles prefer to live in hot habitat with high sulfur contents such as volcanoes. Sulfolobus was the first types of hyperthermoph...

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