Role of Microorganisms in Various Processes - Assignment Example

1. Briefly the role microorganisms play in each of the following: (10 points) a. biological control of pests Microorganisms can be used for controlling pests and hence, can replace chemical pesticides. Some bacteria and viruses, which are pathogenic to insects, are used in pest control. For example, a bacterium Bacillus thuringiensis is used in the biological control of pests such as bollworms, cabbageworms, alfalfa caterpillars etc. This bacterium produces a protein called the Bt-toxin, which is harmful to leaf-eating larvae of these insects. Since microbial pesticides are of biological origin, they do not harm the environment. Moreover, unlike chemical pesticides, microbial pesticides do not persist in the environment. b. recycling of elements Microorganisms are responsible for recycling of vital elements. They convert elements from one form to another, making them available for plants and other organisms. They are important constituents of the food chain as they degrade dead animals and plants. They recycle vital elements such as carbon, nitrogen and sulfur across the environment, between soil and the atmosphere. For example, nitrogen-fixing bacteria, nitrifying bacteria and denitrifying bacteria play an important role in the recycling of nitrogen via the nitrogen cycle. c. normal microbiota The term “normal microbiota” refers to those microorganisms that inhabit the body of a host without causing any harm. In fact, normal microbiota are found to be beneficial to their hosts. For example, some normal microbiota produce B vitamins apart from vitamin K. They also protect their host from other harmful microorganisms by preventing their growth. d. sewage treatment Since microorganisms degrade organic matter, they are used for sewage treatment. Microorganisms grow on the organic matter present in sewage and degrade it into simpler by-products such as methane, carbon dioxide, nitrates, ammonia and other inorganic compounds. Thus by cleaning sewage, microbes help in the recycling of water. e. human insulin production Microorganisms such as Escherichia coli are used in recombinant DNA technology to produce human insulin and other products of human origin. Recombinant DNA is produced by inserting human insulin genes in the E. coli genome. This DNA is then transferred into the bacteria for the production of large amounts of human insulin from E. coli. f. vaccine production Vaccines are produced from microorganisms. Disease causing pathogens are rendered inactive and avirulent by chemical or other treatments. These are then injected into animals and humans to induce immunity against them. Apart from attenuated microorganisms, bacterial and viral proteins and polysaccharides are also used to induce immunity. Thus, microorganisms are also used for prophylactic purposes. g. biofilms Biofilms are formed when microorganisms interact with each other, forming layers on other surfaces. By developing biofilms, microorganisms create their own niches almost anywhere. Biofilms make it difficult to eliminate microorganisms as they protect microbial colonies from disinfectants and antibiotics. They are persistent in medical equipment, water pipes, contact lenses etc, and so, pose a threat to human health. 2. Compare and contrast among DNA, RNA and ATP. In your answer, include both structural and functional information. (10 points) Structural similarities between DNA, RNA and ATP: DNA, RNA and ATP have a nitrogenous base attached to a pentose sugar. Furthermore, in all these three molecules, the sugar is linked to a phosphate group. Structural differences between DNA, RNA and ATP: DNA and RNA are polymers of many nucleotides while each ATP molecule is made of a single nucleotide. The pentose sugar in RNA is a ribose while the pentose sugar in DNA is a deoxyribose, lacking an oxygen atom at the 2’ position. The pentose sugar in ATP is also a ribose sugar. Another difference is that while both DNA and RNA contain many nucleotides that have single phosphate groups linked to the phosphate groups of other nucleotides forming a phosphate backbone, each ATP molecule has three phosphate groups. The nitrogenous bases in DNA are Adenine, Guanine, Thymine and Cytosine. RNA has the same nitrogenous bases as DNA except that Thymine is replaced with Uracil. ATP has only one nitrogenous base – Adenine. DNA is double-stranded while RNA is single-stranded. The two double strands in DNA are held together by hydrogen bonding between the nitrogenous bases of the two different strands, while RNA has hydrogen bonds between nitrogenous bases of the same strand. Functional similarities between DNA, RNA and ATP: There are no functional similarities between the three molecules. Functional differences between DNA, RNA and ATP: DNA stores genetic information while RNA enables the use of this stored information for the production of proteins. DNA is transcribed to RNA, which is then translated into proteins. RNA has also been found to possess enzymatic activity, which is absent in DNA and ATP. ATP molecules store and transfer energy. This activity is absent in RNA and DNA. 3. Write the differences between prokaryotic and eukaryotic cells and give an example for each type of cell. (10 points) The major differences between prokaryotic and eukaryotic cells are given below: Prokaryotic Cells Eukaryotic cells 1) The DNA in prokaryotic cells is not enclosed in a membrane. The DNA in eukaryotic cells is enclosed in a membrane. This membrane is called the nuclear membrane and encloses the nucleus, which is a cell organelle. 2) The DNA is circular. DNA is linear. 3) DNA is present in the form of a single chromosome. (Exceptions: Vibrio cholerae has two chromosomes, a few bacteria are found to have linear chromosomes) DNA is arranged in the form of multiple chromosomes. 4) DNA is not associated with histone proteins but with other proteins. DNA is associated with histone proteins as well as other non-histone proteins. 5) Membrane enclosed cell organelles are absent. Several membrane enclosed cell organelles are present. For example, lysosomes, mitochondria, Golgi bodies etc. 6) Cell wall is made of complex polysaccharides like peptidoglycans. Cell walls are not always present (for example, animal cells lack cell walls). If present, cell walls are chemically and structurally simple and lack peptidoglycan. 7) Binary fission is the usual process of cell division. It is simpler and involves very few processes. Cell division occurs by mitosis. 8) Ribosomes are 70S. Ribosomes are 80S. Example of prokaryotic cells: Bacteria (e.g. Eschericia coli) Example of eukaryotic cells: Animal cells and plant cells, protozoans such as paramecium 4. Draw the following bacterial shapes: (6 points) a. spiral b. bacillus c. Coccus d. spirochetes e. streptobacilli f. staphylococci 5. Compare and contrast the following: (6 points) a. simple diffusion and facilitated diffusion Similarities: Both simple and facilitated diffusion involve the transport of substances across a membrane. Energy is not expended in both these processes, and so these are passive. In both these types of diffusion, substances are transported from high concentration regions to low concentration regions, i.e. down the concentration gradient. Both are reversible processes. Differences: Simple diffusion occurs without the help of any protein transporter. It occurs across the phospholipid bilayer or a semi-permeable membrane. Facilitated diffusion requires the help of transporter proteins called channel proteins or carrier proteins. Small molecules such as H2O are transported by simple diffusion while large polar molecules are transported by facilitated diffusion. b. active transport and facilitated diffusion Similarities: Molecules are transported across a membrane in both processes. Carrier proteins are required for transport in both the processes. Differences: Energy is required for active transport while facilitated diffusion does not require energy. Facilitated diffusion occurs down the concentration gradient, where molecules are transported from regions of high concentrations to regions of low concentrations. Active transport occurs against the concentration gradient where molecules are transported for low concentration regions to high concentration regions. c. active transport and group translocation Similarities: Both processes require energy and so, are active processes. Molecules are transported against a concentration gradient from low to high concentration regions. Transporter proteins are required in both types of transport. Differences: The molecules that are transported across a membrane are not modified in active transport, whereas, they are chemically modified during group translocation. Group translocation requires a complex system of enzymes and transporter proteins, unlike active transport. 6. Describe the use of a DNA probe and PCR for: (6 points) a. Rapid identification of an unknown bacterium Unknown bacteria can be rapidly identified using advanced molecular biology techniques. Of these, PCR and nucleic acid hybridization are the most widely used techniques. Once an unknown bacterium is isolated, its DNA is extracted and amplified using PCR (Polymerase Chain Reaction). Minute quantities of bacterial DNA can be amplified to sufficiently large amounts using PCR, which amplifies the required DNA sequences. After the amplification of DNA of an unknown bacterium, it can be analyzed to see if it has sequences that are similar to other bacteria. DNA probes are fluorescently labeled DNA single-strands of known sequences and belong to known bacteria. The extracted and amplified DNA of unknown bacteria is first denatured to separate the double strands. This DNA is then mixed with the probe and is allowed to hybridize. If the DNA of the unknown bacteria contains sequences complementary to those of the probe, it hybridizes with the probe. By analyzing the fluorescence, it can be estimated whether the DNA of unknown bacteria has bound to the probe or not. If it does, the organism can be easily identified as the one to whom the probe belongs. b. Determining which of a group of bacteria are most closely related. Molecular biology has made it easier to identify closely related bacteria and study evolutionary relationships. This is possible because of the presence of ribosomal RNA (rRNA). rRNA sequences have been conserved across time and have been retained with very little changes during the process of evolution. For determining which of a group of bacteria are most closely related, their DNA can be extracted and amplified by PCR. PCR enables the amplification of required sequences, such as the rDNA sequences in this case, which can then be compared with those of other bacteria using probes. RT-PCR enables the amplification of rRNA using DNA sequences. The bacteria whose rRNA sequences show the highest similarity are said to be most closely related. The DNA or RNA can also be sequenced and compared using online nucleic acid databases to ascertain their identity and evolutionary relationships and for creating phylogenetic trees of closely related species. 7. Compare and contrast each of the following (12 points) a. Cyanobacteria and algae Cyanobacteria are also known as blue green algae. However, they are not algae and are actually photosynthetic bacteria. They are similar to algae as they are green, possess chlorophyll and carry out photosynthesis. A major difference is that algae are eukaryotes while cyanobacteria are prokaryotes. Actinomycetes and Fungi Actinomycetes are gram-positive aerobic bacteria. They are morphologically similar to filamentous fungi. However, their filaments are much smaller in diameter than fungal hyphae. Actinomycetes are prokaryotic whereas fungi are eukaryotic. Like fungi, actinomycetes are also chemoheterotrophs, possess branching hyphae and form spores such as conidia and conidiospores. Bacillus and Lactobacillus Both Bacillus and Lactobacillus belong to the same Class – Bacilli, but to different Orders – Bacillales and Lactobacillales. Both are rod shaped, gram-positive bacteria. Bacillus is usually motile while Lactobacillus is non-motile. Moreover, Bacillus is aerobic, facultative and chemoorganotrophic while Lactobacillus is microaerophilic, facultative and fermentative. Bacillus forms endospores while Lactobacillus is non-sporing. Another difference is that Bacillus is catalase positive while Lactobacillus is catalase negative. Lactobacillus always produces lactic acid by fermentation whereas Bacillus does not. Pseudomonas and Escherichia Both Pseudomonas and Escherichia belong to Class Gamma-Proteobacteria. Both are gram-negative, rod shaped bacteria and cause wound infections. Escherichia is larger than Pseudomonas and has peritrichous flagella while Pseudomonas has polar flagella. Pseudomonas is aerobic while Escherichia is facultatively anaerobic. Rickettsia and Chlamydia Both Chlamydia and Rickettsia are gram-negative, coccoid, non-motile bacteria. They are obligate parasites, and survive and reproduce only within host cells. In the first edition of Bergey’s manual, both Chlamydiae and Rickettsiae were grouped together. However, in the second edition of Bergey’s manual, Rickettsiae have been placed in Class Alpha-Proteobacteria while Chlamydiae have been placed in Phylum Chlamydiae because of differences in their 16S rRNA. Rickettsiae multiply by binary fission while Chlamydiae undergo a different developmental cycle that involves the formation of elementary bodies and reticulate bodies. Ureaplasma and Mycoplasma Ureaplasma and Mycoplasma belong to the order Mycoplasmatales in the Class Mollicutes. They lack cell walls made of peptidoglycans and are usually spherical in shape. Moreover, both are human pathogens. Both Ureaplasma and Mycoplasma are similar in almost all respects except that Ureaplasma can metabolize urea and carries out urea hydrolyis. 8. A mixed culture of Escherichia coli and Penicillium chrysogenum is inoculated onto the following culture media. On which medium would you expect each to grow and why? (6 points) a. 0.5% peptone in tap water Escherichia coli will grow in this media. This is because it is a bacterium and bacteria grow faster than fungi. E. coli, which is a bacterium, will thus overgrow the fungus Penicillium chrysogenum. Moreover, E. coli does not require any growth factors and so, it will be able to grow well in the medium containing only peptone and tap water. Its nitrogen requirements will be met with peptone and carbon and other requirements will be met by small amounts of organic matter in tap water. Another reason for the overgrowth of E. coli is that the breakdown of peptone will produce alkalis that will raise the pH of the medium to basic. Since fungi grow best at a slightly acidic pH, the fungi Penicillium chrysogenum will not grow optimally in this basic medium. b. 10% glucose in tap water. Penicillium chrysogenum will grow in this media, as the high concentration of glucose will inhibit the growth of bacteria. High sugar concentration increases the osmotic pressure of the medium, which is harmful for bacterial growth. In the presence of high sugar or salt concentrations, bacterial cells rupture because of increased flow of water to the outside of the cell, leading to osmotic lysis. This occurs because the concentration of solutes is higher outside the cells than inside, leading to diffusion of water towards the outside. Fungi are resistant to high osmotic pressures and so, survive high sugar and salt concentrations. Therefore, Penicillium chrysogenum will grow in this medium while Escherichia coli will be inhibited. Read More