Microbial ecology history, object of study and applications

The microbial ecology is a discipline of environmental microbiology that arises from the application of ecological principles to microbiology (mikros: small, bios: lifetime, logos: study).

This discipline studies the diversity of microorganisms (microscopic unicellular organisms from 1 to 30 µm), the relationships between them with the rest of living beings and with the environment.

Since microorganisms represent the largest terrestrial biomass, their ecological activities and functions profoundly affect all ecosystems..

The early photosynthetic activity of cyanobacteria and the consequent accumulation of oxygen (O_two) in the primitive atmosphere, represents one of the clearest examples of microbial influence in the evolutionary history of life on planet Earth.

This, given that the presence of oxygen in the atmosphere, allowed the appearance and evolution of all existing aerobic life forms..

Microorganisms maintain a continuous and essential activity for life on Earth. The mechanisms that maintain the microbial diversity of the biosphere are the basis of the dynamics of terrestrial, aquatic and aerial ecosystems..

Given its importance, the possible extinction of microbial communities (due to contamination of their habitats with industrial toxic substances), would generate the disappearance of ecosystems dependent on their functions..

Article index

• 1 History of microbial ecology
  • 1.1 Principles of ecology
  • 1.2 Microbiology
  • 1.3 Microbial ecology
• 2 Methods in microbial ecology
• 3 Sub-disciplines
• 4 Study areas
• 5 Applications
• 6 References

History of microbial ecology

Principles of ecology

In the first half of the 20th century, the principles of general ecology were developed, considering the study of "higher" plants and animals in their natural environment..

Microorganisms and their ecosystem functions were then ignored, despite their great importance in the ecological history of the planet, both because they represent the largest terrestrial biomass and because they are the oldest organisms in the evolutionary history of life on Earth..

At that time, microorganisms were only considered as degraders, mineralizers of organic matter and intermediaries in some nutrient cycles..

Microbiology

It is considered that the scientists Louis Pasteur and Robert Koch founded the discipline of microbiology, by developing the technique of axenic microbial culture, which contains a single cell type, descendant of a single cell.

However, in axenic cultures the interactions between microbial populations could not be studied. It was necessary to develop methods that would allow the study of microbial biological interactions in their natural habitats (essence of ecological relationships).

The first microbiologists to examine interactions between microorganisms, in the soil and interactions with plants, were Sergéi Winogradsky and Martinus Beijerinck, while the majority focused on studying axenic cultures of microorganisms related to diseases or fermentation processes of commercial interest..

Winogradsky and Beijerinck studied in particular the microbial biotransformations of inorganic nitrogen and sulfur compounds in the soil..

Microbial ecology

In the early 1960s, in the era of concern for environmental quality and the polluting impact of industrial activities, microbial ecology emerged as a discipline. The American scientist Thomas D. Brock, was the first author of a text on the subject in 1966.

However, it was at the end of the 1970s when microbial ecology was consolidated as a multidisciplinary specialized area, since it depends on other scientific branches, such as ecology, cellular and molecular biology, biogeochemistry, among others..

The development of microbial ecology is closely related to methodological advances that allow studying the interactions between microorganisms and biotic and abiotic factors in their environment..

In the 1990s, molecular biology techniques were incorporated into the study including in situ of microbial ecology, offering the possibility of exploring the vast biodiversity existing in the microbial world and also knowing its metabolic activities in environments under extreme conditions.

Subsequently, recombinant DNA technology allowed important advances in the elimination of environmental pollutants, as well as in the control of commercially important pests..

Methods in microbial ecology

Among the methods that have allowed the study in situ of microorganisms and their metabolic activity, are:

• Confocal laser microscopy.
• Molecular tools such as fluorescent gene probes, which have allowed the study of complex microbial communities.
• Polymerase Chain Reaction (PCR).
• Radioactive markers and chemical analyzes, which allow the measurement of microbial metabolic activity, among others.

Sub-disciplines

Microbial ecology is usually divided into sub-disciplines, such as:

• The autoecology or ecology of genetically related populations.
• The ecology of microbial ecosystems, which studies the microbial communities in a particular ecosystem (terrestrial, aerial or aquatic).
• Microbial biogeochemical ecology, which studies biogeochemical processes.
• Ecology of host-microorganism relationships.
• Microbial ecology applied to environmental pollution problems and in the restoration of ecological balance in intervened systems.

Study areas

Among the areas of study of microbial ecology are:

• Microbial evolution and its physiological diversity, considering the three domains of life; Bacteria, Archea and Eucaria.
• Reconstruction of microbial phylogenetic relationships.
• Quantitative measurements of the number, biomass and activity of microorganisms in their environment (including non-culturable ones).
• Positive and negative interactions within a microbial population.
• Interactions between different microbial populations (neutralism, commensalism, synergism, mutualism, competition, amensalism, parasitism, and predation).
• Interactions between microorganisms and plants: in the rhizosphere (with nitrogen-fixing microorganisms and mycorrhizal fungi), and in plant aerial structures.
• Phytopathogens; bacterial, fungal and viral.
• Interactions between microorganisms and animals (mutualistic and commensal intestinal symbiosis, predation, among others).
• The composition, functioning and the processes of succession in microbial communities.
• Microbial Adaptations to Extreme Environmental Conditions (Study of Extremophilic Microorganisms).
• The types of microbial habitats (atmosphere-ecosphere, hydro-ecosphere, litho-ecosphere and extreme habitats).
• Biogeochemical cycles influenced by microbial communities (cycles of carbon, hydrogen, oxygen, nitrogen, sulfur, phosphorus, iron, among others).
• Various biotechnological applications in environmental problems and of economic interest.

Applications

Microorganisms are essential in the global processes that allow the maintenance of environmental and human health. In addition, they serve as a model in the study of numerous population interactions (for example, predation).

The understanding of the fundamental ecology of microorganisms and their effects on the environment has made it possible to identify biotechnological metabolic capacities applicable to different areas of economic interest. Some of these areas are mentioned below:

• Control of biodeterioration by corrosive biofilms of metallic structures (such as pipelines, radioactive waste containers, among others).
• Pest and pathogen control.
• Restoration of agricultural soils degraded by overexploitation.
• Biotreatment of solid waste in composting and landfills.
• Biotreatment of effluents, through wastewater treatment systems (for example, using immobilized biofilms).
• Bioremediation of soils and waters contaminated with inorganic substances (such as heavy metals), or xenobiotics (toxic synthetic products, not generated by natural biosynthetic processes). These xenobiotic compounds include halocarbons, nitroaromatics, polychlorinated biphenyls, dioxins, alkylbenzyl sulfonates, petroleum hydrocarbons, and pesticides..

• Biorecovery of minerals through bioleaching (for example, gold and copper).
• Production of biofuels (ethanol, methane, among other hydrocarbons) and microbial biomass.

References

1. Kim, M-B. (2008). Progress in Environmental Microbiology. Myung-Bo Kim Editor. pp 275.
2. Madigan, M. T., Martinko, J. M., Bender, K.S., Buckley, D. H. Stahl, D. A. and Brock, T. (2015). Brock biology of microorganisms. 14 ed. Benjamin Cummings. pp 1041.
3. Madsen, E. L. (2008). Environmental Microbiology: From Genomes to Biogeochemistry. Wiley-Blackwell. pp 490.
4. McKinney, R. E. (2004). Environmental Pollution Control Microbiology. M. Dekker. pp 453.
5. Prescott, L. M. (2002). Microbiology. Fifth edition, McGraw-Hill Science / Engineering / Math. pp 1147.
6. Van den Burg, B. (2003). Extremophiles as a source for novel enzymes. Current Opinion in Microbiology, 6 (3), 213-218. doi: 10.1016 / s1369-5274 (03) 00060-2.
7. Wilson, S. C., and Jones, K. C. (1993). Bioremediation of soil contaminated with polynuclear aromatic hydrocarbons (PAHs): A review. Environmental Pollution, 81 (3), 229-249. doi: 10.1016 / 0269-7491 (93) 90206-4.