However; there are many microbes that are damaging to society. Certain microbes cause disease to humans, many proving fatal. Diseases affect crops and livestock that humans rely upon for a living and many microbes are damaging to the environment.
This report identifies both the positive and negative impacts of microbes, and how their existence can be influenced by human activities.
2. POSITIVE AND NEGATIVE EFFECTS OF MICROBES
2.1. Negative effects
Microbes interact with other organisms in both positive and negative ways. ‘The term symbiosis is used to denote any intimate relationship between two populations’, (Atlas and Bartha, 1998: 65). Symbiosis could be considered beneficial, as it is a way of maintaining ecological balance; however to an individual it determines whether its species survives or not. A comensal relationship is where one population benefits whilst the other remains unaffected, whereas synergistic or mutual relationships involve both populations benefiting. A parasitic relationship is where one population benefits whilst the other is harmed. It is this relationship that is undesirable in human society due to its negative impacts of disease transmission.
‘Environmental changes appear to be a major cause of the recent emergence of several important infectious human diseases’, (Atlas and Bartha, 1998: 166). Many of these environmental changes have been the result of human activities causing populations of microbes and their vectors to fluctuate. An example of this was in 1961 when an outbreak of the Oropouche virus in Brazil affected 11,000 people. The outbreak was linked to the construction of a highway that channelled deep into the Amazon rainforest. This disruption caused a population explosion of midges that serve as vectors for the Oropouche virus, which then transferred to the highway workers.
Microbes can also cause allergies as well as disease. A study by Pieckova and Jesenska (1999) stated that ‘Alternaria alternate is regarded as the main cause of allergy and asthma in children aged 6- 11 years and to be a xerophilic, xerotolerant and acidophilic fungus’. This mould (pictured in figure 2.1) is found in indoor environments; their spores are liberated into the air and enter the respiratory tract of humans via respiration.
Figure 2.1: Alternaria spp. spores
(Source: http://www.emedicine.com/ped/images/681478mold1-alternaria.jpg)
Humans have used microbes to their advantage for developing drugs (discussed more in section 2.2). However; the coevolution of parasitic microbes means that human behaviour influences how they adapt to survive. This has lead to a rise in drug-resistant mutilations. ‘Antibiotic resistance is selected for when chemotherapy is not completed and when antibiotics are not used correctly’, (Tortora, et al, 2004: 440). When drug levels decrease before the disease has been eradicated from the body, some bacteria survive and reproduce resistant mutants.
A recent example of where drug-resistance has become a major problem is the outbreak of MRSA in hospitals. ‘Methicillin-resistant Staphylococcus aureus (MRSA) (a.k.a Golden Staphylococci) is a specific strain of the Staphylococcus aureus bacterium that has developed antibiotic resistance to all penicillins, including methicillin and other narrow-spectrum β-lactamase-resistant penicillin antibiotics’, (Wikipedia, 2007).
Figure 2.2: Electron Micrograph of MRSA
(Source: )
Although Staphylococcus aureus lives on the skin of humans without causing harm; entering the bloodstream via a wound of an immuno-suppressed patient could prove fatal. MRSA has also shown resistance to most disinfectants, with alcohol being the only proven sanitiser. A study by Neely and Maley (1999) also highlighted that ‘staphylococci and enterococci can survive for days to months after drying on commonly used hospital fabrics and plastics’.
Staphylococcus aureus also affects the food industry. Capable of withstanding high salinity environments, S. aureus thrives on heavily salted foods that would normally be preserved by the high salinity levels.
Another microbe affecting the food industry is the thermophilic fungus Talaromyces macrosporus. Heating food is recommended in order to kill harmful dormant cells (ascospores); however Dijksterhuis and Teunissen (2003) stated that ‘extreme heat and high pressure can activate these cells to germinate’. They are a common contaminant of fruit juices, and can withstand processes such as pasteurisation.
2.2. Positive effects
Microbes can also be beneficial in human society and have positive effects on a number of practises.
Lactobacillus acidophilus is rod-shaped, non-pathogenic bacteria found in dairy products. They are classed as acidophiles as they are resistant to pH values as low as 4. ‘The acid resistance of Lactobacilli enable them to continue growing during natural lactic fermentations when the pH value has dropped too low for other lactic acid bacteria to grow, and the Lactobacilli are therefore responsible for the final stages of most lactic acid fermentations’, (Madigan, et al, 2003: 404). These bacteria are very important to the food industry, and are also present in vinegar, cheese and yogurt.
When consumed, L. acidophilus is beneficial to the body as part of the natural flora in the digestive tract and the genitourinary tract. When present in the mouth and vagina, L. acidophilus help control levels of pathogenic microbes such as Candida (thrush) by lowering the pH level of the environment. These undesirable microbes are unable to survive at such low pH levels.
Figure 2.3: L. acidophilus
(Source: http://elementy.ru/images/news/lactobacillus_acidophilus_300.jpg)
Microbes are also beneficial to the medical industry in controlling other undesirable microbes. Penicillium is a fungal microorganism that has been used to produce the antibiotic penicillin, which destroys microbial cells. ‘Penicillins prevent the cross-linking of the peptidoglycans, which interferes with the final stages of the construction of the cell wall’, (Tortora, et al, 2004: 568). Natural penicillin is a narrow spectrum antibiotic, which can mean gram-negative bacteria are not as susceptible as gram-positive bacteria due to their extra outer membrane. However; semisynthesised penicillin are broad spectrum, containing natural penicillin plus other effective chemicals, and are therefore active against gram-negative bacteria.
A disadvantage of antibiotics is that they also kill the beneficial gut flora such as L. acidophilus mentioned earlier. ‘Disruption of the normal microbiota can increase the host’s susceptibility to invasions by opportunistic pathogens’, (Atlas and Bartha, 1998: 630).
Another way microbes are beneficial to the medical industry is in the production of vaccinations. These are used as preventative methods against a number of human and animal diseases. ‘Vaccines normally contain antigens as killed non-infectious pathogens or as live pathogens of attenuated virulence’, (Atlas and Bartha, 1998: 626). An example of a commonly administered vaccine is the tetanus vaccine; this allows the host to produce an immune response to the bacterium Clostridium tetani.
In agriculture, a process of producing a low-cost, protein-rich animal feed is assisted by fungal microbes. ‘This process involves the conversion of cassava starch to microbial biomass protein (MBP) through the nonaseptic growth of the amylolytic, acidophilic, thermophilic fungus Cephalosporium eichhorniae 152’, (Stevens and Gregory, 1986). The acidophilic nature of these fungi indicates that they would not be opportunist pathogens, and the feed processed has a high nutritional value.
Microbes can also be utilised to produce energy as mentioned in section 1.2. There has been interest in using the strain of green algae Botryococcus braunii as a renewable method of producing petroleum. Madigan, et al, (2003) stated that ‘in the colonial algae B. braunii, growth of the algae is accompanied by the excretion of long-chain hydrocarbons that have the consistency of oil’. Figure 2.4 demonstrates oil droplets being excreted by the algae.
Figure 2.4: Oil droplets excreted by B. braunii
(Source: Madigan, et al, 2003: 675)
3. BIOREMEDIATION
‘In 1988, scientists began using microbes to clean up pollutants and toxic wastes produced by various industrial processes’, (Tortora, et al, 2004: 17). This process, known as bioremediation, involves microbes consuming pollutants to use as energy sources or producing enzymes that break down harmful substances.
Using microbes to clean up oils spills and degrade petroleum is considered economic and environmentally important. When storing oils and petroleum microbial growth is undesirable; however in environmentally disastrous situations such as oil spills, microbial utilisation is invaluable. ‘Several strains of the bacterium Pseudomonas occur naturally and can be used in a mixture to clean up oil-contaminated water’, (Lowrie and Wells, 1994: 87). Other microbes have been shown to oxidise hydrocarbons in oil, including fungi, cyanobacteria, green algae and many species of bacteria. Figure 3.1 shows hydrocarbon-oxidising bacteria involved in decomposing oil droplets.
Figure 3.1a: Hydrocarbon-oxidising bacteria concentrated at the oil-water interface
(Source: Madigan, et al, 2003: 674)
Figure 3.1b: Exxon Valdez oil spill- arrow indicates rectangular plot treated with inorganic nutrients to stimulate Hydrocarbon-oxidising bacteria
(Source: Madigan, et al, 2003: 675)
The Wheal Jane incident in January 1992 involved the Fal Estuary in Cornwall being accidentally polluted with acidic (pH 3.1) metal-laden mine water. The mine water was less dense than the estuary water, and therefore carried a very visual orange tide that caused public concern as shown in figure 3.2.
Figure 3.2: Orange tide caused by polluted mine water in the Fal Estuary
(Source: http://www.projects.ex.ac.uk/geomincentre/estuary/Main/jane.htm)
‘The engineering treatment of the mine water discharge from Wheal Jane has cost in excess of £20 million’, (: 10). It has involved the planting of reed beds to remove iron hydroxide/ oxyhydroxide and arsenic; and the use of anaerobic cells and rock filters that have removed other metals by promoting the growth of beneficial bacteria and algae. Figure 3.3 demonstrates how this organic bioremediation treatment worked.
Figure 3.3: The Wheal Jane Pilot Passive Treatment Plant
(Source: http://www.earth.ucl.ac.uk/department/collections/RockRoom/econo.htm)
Microbes have also been used to clean up sites where it would be dangerous for humans to enter. A useful extremophilic bacterium known as Deinococcus radiodurans is the most radio-resistant organism known, and can be used to clean up solvents and heavy metals in radioactive environments. This has proved very useful in detoxifying ionic mercury found in radioactive waste generated from nuclear weapons manufacture.
Acidophilic bacteria of the genus Thiobacillus are also recruited to extract valuable metals from low-grade ore in a process known as microbial leaching. Copper and uranium have exploited Thiobacillus for copper and uranium mining. By using water, moisture activates the already present bacteria to oxidise sulphur which binds copper and uranium in the ore. ‘Sulphuric acid is produced during the process, yet the organism is able to flourish in these conditions’, (Lowrie and Wells, 1994: 86). Thiobacillus spp. have also been used to accumulate silver in a process known as bioaccumulation; as well as Pseudomonas spp. being used to accumulate mercury and uranium. Figure 3.4 shows a leaching dump where low-grade ore has been crushed.
Figure 3.4: Leaching dump
(Source: Madigan, et al, 2003: 670)
4. CONCLUSION
This report highlights the significance of microorganisms for the existence of life on Earth, and how they can both benefit and hinder human society. They are the oldest life forms on the planet, and without them human society would not exist.
Microbes assist human activities in many ways; both naturally and through deliberate manipulation. Section 1 highlights how microbes assist the balance of the environment via the recycling of nutrients, and how all plants/ animals/ humans rely on microbial existence for forming food chains and energy sources. It also highlights the great diversity of microbial uses, and how human manipulation has allowed them to aid many industries such as food production, pharmaceutical production, agriculture, etc. However; both section 1.2 and section 2.1 identify how many microbes are undesirable in human society by causing disease, food spoilage, industrial damage, etc. Whilst section 2.2 highlights how humans have used microbes to counteract disease, it is disease that controls populations and is a natural way of preventing the planet from becoming over-crowded. Whilst human activities will continue to interfere with diseases, the evolutionary arms race will ensure that resistant mutations will evolve.
Section 3 highlights how the state of the environment may depend on processes such as bioremediation in order to reduce pollution. Although this is of great importance, Lowrie and Wells (1994) stated that ‘it is unlikely that bacteria could ever cope fully with a major oil pollution disaster, such as the deliberate release of crude oil…’ This is because microbes cannot access through the whole oil slick, and temperature can affect their effectiveness. Low temperature in parts of the world, such as in Alaska where the Exxon Valdez oil tanker disaster occurred, may affect the productivity of certain strains. Efforts still need to be put in place in terms of preventative measures rather than solutions when it comes to environmental pollution.
5. REFERENCES AND BIBLIOGRAPHY
5.1 References
Atlas, R.M., and Bartha, R. (1998) Microbial Ecology: Fundamentals and Applications, 4th Ed. USA: Benjamin/ Cummings Publishing Company, Inc: 27, 28, 65, 166, 556, 626, 630.
Dijksterhuis, J., and Teunissen, P.G.M. (2004) Dormant ascospores of Talaromyces macrosporus are activated to germinate after treatment with ultra high pressure. In Journal of Applied Microbiology, 96: 162.
Lowrie, P., and Wells, S. (1994) Microbiology and Biotechnology, Great Britain: Cambridge University Press: 38, 57, 86, 87.
Madigan, M.T., Martinko,J.M., and Parker, J. (2003) Brock Biology of Microorganisms, 10th Ed. USA: Pearson Education, Inc: 1, 8, 404.
Neely, A.N., and Maley, M.P. (1999) Survival of Enterococci and Straphylococci on Hospital Fabrics and Plastic. In Journal of Clinical Microbiology, 38: 724- 726.
Pieckova, E., and Jesenska, Z. (1999) Microscopic Fungi in dwellings and their health implications in humans. In Ann Agric Environ Med, 6: 1-11.
Prescott, L.M., Harley, J.P., and Klein, D.A. (2005) Microbiology, 6th Ed. New York: McGraw- Hill, Inc: 967.
Stevens, C.A., and Gregory, K.F. (1986) Production of Microbial Biomass Protein from Potato Processing Wastes by Cephalosporium eichhorniae. In Applied and Environmental Microbiology, 53: 284- 291.
Tortora, G.J., Funke, B.R., and Case, C.L. (2004) Microbiology: An introduction, 8th ed. USA: Pearson Education, Inc.
Wikipedia (2007) Methicillin- Resistant Straphylococcus aureus (online). Available from <http://en.wikipedia.org/wiki/Methicillin-resistant_Staphylococcus_aureus> (Accessed 3rd January 2007).
Younger, P.L. 2002. Mine water pollution from Kernow to Kwazulu-Natal: geochemical remedial options and their selection in practice. Geoscience in south-west England, 10.
5.2 Bibliography
Astrobiology (2005) Life in extreme environments (online) Available from <http://www.astrobiology.com/extreme.html> (Accessed 3rd January 2007).
Bacteria Museum (2005) Extremophiles (online) Available from <http://www.bacteriamuseum.org/niches/evolution/extremophiles.shtml> (Accessed 21st December 2006).
NHS Direct (2006) MRSA (online) Available from <http://www.nhsdirect.nhs.uk/articles/article.aspx?articleId=252> (Accessed 21st December 2006).
Think Quest Library (nd) Extremophiles (online) Available from <http://library.thinkquest.org/CR0212089/home.htm> (Accessed 22nd December 2006).
The Microbial World (nd) Penicillin and other antibiotics (online) Available from <http://helios.bto.ed.ac.uk/bto/microbes/penicill.htm#Penicillin:%20the%20story%20of%20an%20antibiotic> (Accessed 4th January 2007).
The University of Exeter (2007) The Wheal Jane incident and water quality (online) Available from <http://www.projects.ex.ac.uk/geomincentre/estuary/Main/jane.htm> (Accessed 3rd January 2007).
UCL Department of Earth Sciences (2007) Economic Geology (online) Available from <http://www.earth.ucl.ac.uk/department/collections/RockRoom/econo.htm> (Accessed 3rd January 2007).
Wikipedia (2007) Deinococcus radiodurans (online) Available from <http://en.wikipedia.org/wiki/Deinococcus_radiodurans> (Accessed 4th January 2007).
6. LIST OF FIGURES
Front cover picture:
Figure 1.1: Evolutionary events of Microorganisms
Atlas, R.M., and Bartha, R. (1998) Microbial Ecology: Fundamentals and Applications, 4th Ed. USA: Benjamin/ Cummings Publishing Company, Inc: 28.
Figure 1.2: Diversity of Biotechnology
Madigan, M.T., Martinko,J.M., and Parker, J. (2003) Brock Biology of Microorganisms, 10th Ed. USA: Pearson Education, Inc: 6.
Figure 2.1: Alternaria spores (2005) E-medicine (online) Available from <http://www.emedicine.com/ped/images/681478mold1-alternaria.jpg> (Accessed 12th January 2007).
Figure 2.2: Electron Micrograph of MRSA (2007) Methicillin-Resistant Straphylococci aureus (online) Available from <http://en.wikipedia.org/wiki/Methicillin-resistant_Staphylococcus_aureus> (Accessed 3rd January 2007).
Figure 2.3: L. acidophilus (2005) (online) Available from: <http://elementy.ru/images/news/lactobacillus_acidophilus_300.jpg> (Accessed 23rd December 2006).
Figure 2.4 Oil droplets excreted by B. Braunii
Madigan, M.T., Martinko,J.M., and Parker, J. (2003) Brock Biology of Microorganisms, 10th Ed. USA: Pearson Education, Inc: 675.
Figure 3.1: Hydrocarbon-oxidising bacteria
Madigan, M.T., Martinko,J.M., and Parker, J. (2003) Brock Biology of Microorganisms, 10th Ed. USA: Pearson Education, Inc: 674- 5.
Figure 3.2: Orange tide caused by polluted water in the Fal Estuary
The University of Exeter (2007) The Wheal Jane incident and water quality (online) Available from <http://www.projects.ex.ac.uk/geomincentre/estuary/Main/jane.htm> (Accessed 3rd January 2007).
Figure 3.3: The Wheal Jane Pilot Passive Treatment Plant
UCL Department of Earth Sciences (2007) Economic Geology (online) Available from <http://www.earth.ucl.ac.uk/department/collections/RockRoom/econo.htm> (Accessed 3rd January 2007).
Figure 3.4: Leaching dump
Madigan, M.T., Martinko,J.M., and Parker, J. (2003) Brock Biology of Microorganisms, 10th Ed. USA: Pearson Education, Inc: 670.