A review of positive and negative impacts of microbes on the environment

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A REVIEW OF POSITIVE AND NEGATIVE IMPACTS OF MICROBES IN THE ENVIRONMENT

1. INTRODUCTION

 

1.1. Microbes in the environment

‘Microbiology is the study of microorganisms, a large and diverse group of microscopic organisms that exist as single cells or cell clusters; it also includes viruses which are microscopic but not cellular’, (Madigan, Martinko and Parker, 2003: 1). It consists of prokaryotic organisms such as bacteria and archaebacteria; and eukaryotic organisms such as fungi, protozoa and algae.

Microbiologists have evidence that microbes are the oldest life forms on earth. ‘Isotopic ratios and microfossils indicate that chemical evolution led to primitive forms of prokaryotic life less than 1 billion years after the formation of Planet Earth, which is 4.5 billion years old’, (Atlas and Bartha, 1998: 27).

Figure 1.1 shows the evolutionary events of microorganisms over the last 4 billion years.

Figure 1.1: Evolutionary events of Microorganisms

(Source: Atlas and Bartha, 1997: 28)

 

The human race, and many other higher life forms, owes its existence to microbial activity 10,000 years ago when cyanobacteria fixed oxygen in the atmosphere. Figure 1.1 highlights how biodiversity has gradually increased since anaerobic bacteria evolved.

Scientific evidence shows that the sun’s temperature has increased by 30% during the past 4-5 billion years. By microbial activity changing original carbon dioxide to the present oxygen atmosphere, temperature remains around 13ºC, whereas a lifeless earth would be around 250ºC.

1.2. Microbes and Biotechnology

‘The majority of microorganisms make crucial contributions to the welfare of the world’s inhabitants by helping to maintain the balance of living organisms and chemicals in the environment’, (Tortora, Funke and Case, 2004: 1). They form the basis of the food chains, break down waste and recycle chemical elements such as nitrogen and phosphorus. Microbes such as unicellular algae have a role in photosynthesis, and many microbes live in the digestive of humans/ animals to aid digestion and synthesise certain vitamins.

‘Biotechnology is the application of biological systems, organisms or processes in manufacturing or service industries…it is a composite science, involving microbiology, genetics, biochemistry and engineering’, (Lowrie and Wells, 1994:38).

Figure 1.2 shows the diversity of biotechnology

Figure 1.2: Diversity of Biotechnology

(Source: Madigan, et al, 2003: 6)

Although biotechnology is a recent technology, its principles have been applied throughout history through beer brewing and bread making. Modern biotechnology utilises microorganisms in large scale industrial processes such as new ways to produce energy and advances in the medical industry. These principles involve the exploitation of the chemistry of microbes to produce a certain product or desired effect. DNA within individual microbes can be manipulated to produce maximum desired effects, and this process is called genetic engineering. Genes from certain microbes can also be transferred to another type of microbe, which is known as DNA expression. ‘DNA expression in different organisms can improve production efficiency and minimise the purification steps required before the product is ready to use’, (Prescott, Harley and Klein, 2005: 967). These techniques have been used widely in the medical industry to produce pharmaceuticals, which is discussed more in section 2.2. These techniques have also been used in agriculture to manipulate plant genes. ‘The new plants may have an increased resistance to disease or pest attack or an enhanced capacity for nitrogen fixation’, (Lowrie and Wells, 1994: 57). Quality and shelf life of the food produced by these crops is also improved.

The manipulation of genes has also been applied to livestock to increase productivity through high yielding breeds. Antibiotic growth hormones allow livestock to grow in the fastest time at the minimalist cost. Bacteria such as Lactobacillus plantarum in livestock silage enhance production also.

As mentioned earlier, microbes have an important role in breaking down waste. Biotechnology has exploited this process for creating energy which can be converted into biofuels. ‘Microbial biomass and existing waste materials such as domestic refuse, surplus grain and animal wastes, can be converted into biofuels, such as methane and ethanol, by the degradative activities of microorganisms’, (Madigan, et al, 2003: 8). It is some of these microbes that have been isolated for pollution prevention and site remediation which has lead to a process known as bioremediation. ‘When bioremediation is applicable, it is often a cost-effective means of restoring environmental quality’, (Atlas and Bartha, 1998: 556). This is discussed in more detail in section 3.

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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 ...

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