Archaea as a Group of Single-Celled Microorganisms - Essay Example

Table of Contents 1. Introduction……………………………………………………………………………….3 2. Archaea as Prokaryotes…………………………………………………………………...3 i. Gene Repertoire………………………………………………………………………3 ii. Cellular Size………………………………………………………………………......4 iii. Phylogenetic Tree………………………………………………………………….....5 3. Archaea, Eukaryotes and Bacteria………………………………………………………..5 4. Archaea as Extremophiles………………………………………………………………...7 i. Thermophiles…………………………………………………………………......7 ii. Halophiles………………………………………………………………………...8 iii. Methanogens……………………………………………………………………...8 5. Conclusion…………………………………………………………………………….....10 6. Works Cited……………………………………………………………………………..10 Archaea Introduction Archaea is a group of single-celled microorganisms. Basing on their ssrRNA, Archaea have three phylogenetic groups namely Crenarchaeota, Euryarchaeota and Korarchaeota. Korarchaeota represents archaea species that have undergone little evolution (Sapp, 2009). However, its physiology presents three different types namely the Halophiles, Methanogens and Extreme Thermophile. Their lack of cell nucleus makes it easy for them to thrive in environments with poor survival conditions. For instance, the Halophilic archaea are often found thriving in salty conditions because they have a unique type of genes that encodes the enzymes for the methylaspartate pathway to reduce osmosis. Methanogens produce methane and thermophile Archaea thrive in environments with very high temperatures. Throughout the essay an extensive overview on the reasons as to why the Archaea have been classified as Prokaryotes will give. In addition, the essay covers the evolution of the Archaea and relation to Eukaryotes and Bacteria. Lastly, the discussion will elaborate on the reasons why Archaea are classified as extremophiles. Gottschalk G. (2012). Archaea as Prokaryotes Currently, Archaea is under the prokaryotic domain. Gene Repertoire Archaea and bacteria have a similarity in the cell structure. To be exact, Archaea have shown no difference with the Gram-positive bacteria in terms of cell structure. This could be the reason as to why Archaea is under the prokaryotic domain because is held together by a single unit of a lipid membrane with a very heavy layer sacculus. Outer membrane Cell wall Cell wall cell wall Cell membrane cell membrane Archaea Gram-positive Gram-negative Bacteria bacteria Through the diagrams above, the similarities in the cell structure of the Archaea and Bacteria can be seen. A further link through research has shown that some Archaea species like Viz Thermoplasma contain staining of the Gram-positive bacteria species for instance Viz mycoplasma. Cellular Size Just as most prokaryotes, Archaea has a small cellular size because it lacks the nucleus (Koonin et al., 1997). This makes their locomotion very swift because it can take up the shape of any object. It can also change its form depending on the surrounding to avoid harm. In research findings, it has been established that about 65% of the genes in a species of Archaea M.janaschii are found in most of the bacteria with only 7% being in Eukarya. Even though Archaea shows uniqueness in its gene composition, the same is trend is evident in most prokaryotic genomes. Phylogenetic Tree Basing the argument using the prokaryotic homolog only, then the phylogenetic tree can actually prove that there is a very close relationship between Archaea and Gram-positive bacteria. This however shows that the Gram-negative bacteria have little similarities with the Archea. Signature sequences in the diversty of the protein structure have been used to show the unique relationship between the Gram-positive bacteria and the Archaea. This concept has a biological meaning if the Non Darwinian theories are not included. In addition, Archaea has a high reproductive rate (Kelman L. and Kelman Z, 2004). This characteristic is evident in bacteria and eukarya. Due to their small size and lack of cell structure, reproduction is very simple. Archaea, Eukaryotes and Bacteria In the historical evidence, a researcher by the Carl Woese proved that indeed Archaea, bacteria and eukaryotes currently which different domains had their emergence from a single organism. There are so many explanations regarding the evolution of these domains. Some researchers argue that both bacteria and Archaea generate from the same ancestor; thermophile. Their argument is valid because it shows and relates the reason as to why the Archaea can thrive under very high temperatures. Through evolution, it is easy to understand the similarities and the differences among Archaea, bacteria and Eukarya. The information found in the Archaea gene show that the transformational processes are the basic realities that set in the differences among these domains. Most researchers agree that this assumption was based on the universal ancestor ( Woese &Kandler, 1990).The diagram below is a reflection of what Kandler termed as the universal ancestor. Bacteria Archaea Eukarya From the diagram, three pre-cellular components that represent Bacteria, Archaea and Eukarya appear to lack a general form of chromosome identity. The lack of the cell membrane in all these entities makes it easy for gene transfer across their walls. Researchers attribute to the fact that some of the diversity in bacteria and Archaea has its origin at this pre-cellular stage. However, Gupta views the similarities from a different perspective. To begin with, Archaea shows a high rate of resistance to most of the antibiotics that are made from the gram-positive bacteria. The reaction between the antibiotics and the Archaea wall membrane help define the origin and the growing diverse changes between Archaea and bacteria. Therefore, Gupta’s argument is that if the evolutionary differences and similarities stem at the pre-cellular stage, then understanding the concept of Archaea’s resistance to antibiotics can be very challenging. This argument can as well provide the reason as to why Archaea can thrive in very harsh environments. Therefore, an understanding of the Archaea’s evolution basing on its high resistance to antibiotics reinstates the evidence. Archaea as Extremophiles From the different types of Archaea in the introduction, it was easy to point out the most common habitats that Archaea thrive in. scientific classification of organisms classifies extremophiles in the Kingdom Archae in other words refered to as Archaebacteria. Thermophile thrive under high temperature conditions, halophiles thrive in salty environments and methanogens thrive in oxygen free environments. Already, it sounds like an assumption. Not all extremophiles are found under the Kingdom Archaea. These include bacteria, eukaryotic prokaryotes, and some worm and krill species. From the basic definition, an extremephile Archaea survives under high temperatures with Methanopyrus kandleri being a perfect example. Themophiles Thermophilic Archaea have mechanisms embedded in their membranes that help them to resist high temperatures. Imagine of places like hot springs, hot volcano vents, boiling water but such organisms seek life there. For them to achieve this property, their lipid membrane layers and the crystalline fluid have a high resistance and thus act like a good barrier to the external high temperature. However, permeability and resistance depends with the external temperatures. Therefore, they have to counter immediate temperature changes, thermophilic Archaea have a system that helps them in regulating their fatty acid. Proteins are destroyed when exposed to high temperatures. To counter this, they use “sequence-based mechanism” where their proteins can be transformed to amino acids. In additions, they have di-glycerol-phosphate solutes that prevent their enzymes and proteins from exposure to high temperatures. At the ocean floor lives the Pompeii worm, which has shown the capability to withstand the highest degree of temperature (800c) (Woese and Fox, 1977). Halophiles Halophiles thrive in salty conditions. They have high levels red pigmentation. This is because they are very helpful in converting sunlight to chemical energy, which in other ways help them evade radiation effects. They also have high levels of ion on their external layer, which is very helpful in controlling osmotic processes thus reducing damage. To increase the level of internal osmosis, halophytes have amino acids, which act as compatible solutes in their cytoplasm. Interestingly, none of these processes impairs their cell functioning but offer further protection as well. In addition, they have a unique way of potassium ions selective influx thus moderating the salt level in the cytoplasm. Since they have to increase their salt concentration internally without displacing proteins, halophytes uniquely replace neutral with acidic aspartic amino acids. In terms of structure, they have low hydrophobicity to stabilize the proteins. Methanogens Methanogens survive in environments free from oxygen. They are known for their capability to produce methane gas. This component helps in protecting them from any oxygen presence. A good place for their survival includes the human’s gut. A methaonogen under genus methanobrevibacter is the most common type present in the gut. They have the capacity to reproduce very fast to counter any exposure to oxygen. In the gut, methanogens ferment the ingested food thus making it easy for digestion. In addition, with their capability to oxidize carbon (II) oxide into water, it makes it easy for important metabolic conversions in the body. Class Conditions Adaptations Thermophiles High temeperatures Sequence-based mechanisms Di-glycerol-phosphate solutes Halophiles Salty conditions High levels of red pigmentation, ion concentration Amino Acids Low hydrophobicity Methanogens Oxygen-free zones Produce methane gas Fast rates of reproduction Oxidize CO2 into water Conclusion Like most small organisms, Archaea has for long been confused to be under the bacteria domain. However, through the discussion, a history that elaborates the relationship between Archaea and bacteria makes it easy to understand. There are many similarities as to why it has been confused to be bacteria. Of course, they have some similarities in terms of cell structure, cell size and the theory under the phylogenetic tree. The universal ancestor gives the whole history with an argument in favor to prove that bacteria, archaea and eukarya had the same foundation of life. However, there have been many criticisms that find the universal ancestor invaid through the experiments done. They found that some types of Archaea show resistance to the antibiotics and thus disputing the concept that all these domains share some gene. A number Archae are extrophilic in nature because they have special features that enable them adaptable to these extreme environments. Work cited David M. B. (2010). Archea: Salt-Lovers, Methane-Makers, Thermophiles, and Other Archeans (A Class of Their Own). Crabtree Publishing Company. Sapp Jan.(2009). The New Foundations of Evolution. New York: Oxford University Press. Gottschalk G. (2012). Discover the World of Microbes: Bacteria, Archea, Viruses. David R. B., George G. and Richard W. C. (2012). Bergey’s Manual of Systematic Bacteriology: Volume One: The Archea and the Deeply Branching and Phototrophic Bacteria. New York. Springer. Rodolphe B. and John V. D. O. (2012). CRISPR-Cas Systems: RNA-mediated Adaptive Immunity in Bacteria and Archaea. Springer. David W., James D. and Clay F. (2011). The Physiology and Biochemistry of Prokaryotes. USA. Oxford University Press. Johannes H. P. H. (2010). (Endo)symbiotic Methanogenic Archaea (Microbiology Monographs). Springer. Read More