Environmental microbiology
Environmental microbiology is the study of the composition and physiology of microbial communities in the environment. The environment in this case means the soil, water, air  and sediments covering the planet and can also include the animals and plants that inhabit these areas. Environmental microbiology also includes the study of microorganisms that exist in artificial environments such as bioreactors.
Microbial life is amazingly diverse and microorganisms literally cover the planet. It is estimated that we know fewer than 1% of the microbial species on Earth. Microorganisms can survive in some of the most extreme environments on the planet and some, for example the Archaea, can survive high temperatures, often above 100C, as found in geysers, black smokers, and oil wells. Some are found in very cold habitats and others in highly saline, acidic, or alkaline water.
An average gram of soil contains approximately one billion (1,000,000,000) microbes representing probably several thousand species. Microorganisms have special impact on the whole biosphere. They are the backbone of ecosystems of the zones where light cannot approach. In such zones, chemosynthetic bacteria are present which provide energy and carbon to the other organisms there. Some microbes are decomposers which have ability to recycle the nutrients. Microbes have a special role in biogeochemical cycles. Microbes, especially bacteria, are of great importance because their symbiotic relationship (either positive or negative) have special effects on the ecosystem.
Microorganisms are used for in-situ microbial biodegradation or bioremediation of domestic, agricultural and industrial wastes and subsurface pollution in soils, sediments and marine environments. The ability of each microorganism to degrade toxic waste depends on the nature of each contaminant. Since most sites are typically comprised of multiple pollutant types, the most effective approach to microbial biodegradation is to use a mixture of bacterial species and strains, each specific to the biodegradation of one or more types of contaminants. It is vital to monitor the composition of the indigenous and added bacteria in order to evaluate the activity level and to permit modifications of the nutrients and other conditions for optimizing the bioremediation process.

# Oil biodegradation
Petroleum oil is toxic and pollution of the environment by oil causes major ecological concern. Oil spills of coastal regions and the open sea are poorly containable and mitigation is difficult, however much of the oil can be eliminated by the hydrocarbon-degrading activities of microbial communities, in particular the hydrocarbonoclastic bacteria (HCB). These organisms can help remediate the ecological damage caused by oil pollution of marine habitats. HCB also have potential biotechnological applications in the areas of bioplastics and biocatalysis.

# Degradation of aromatic compounds by Acinetobacter
Acinetobacter strains isolated from the environment are capable of the biodegradation of a wide range of aromatic compounds. The predominant route for the final stages of assimilation to central metabolites is through catechol or protocatechuate (3,4-dihydroxybenzoate) and the beta-ketoadipate pathway and the diversity within the genus lies in the channelling of growth substrates, most of which are natural products of  plant origin, into this pathway.

# Analysis of waste biotreatment
Biotreatment, the processing of wastes using living organisms, is an environmentally friendly alternative to other options for treating waste material. Bioreactors] have been designed to overcome the various limiting factors of biotreatment processes in highly controlled systems. This versatility in the design of bioreactors allows the treatment of a wide range of wastes under optimized conditions. It is vital to consider various microorganisms and a great number of analyses are often required.

# Environmental genomics of Cyanobacteria
The application of molecular biology and genomics to environmental microbiology has led to the discovery of a huge complexity in natural communities of microbes. Diversity surveying, community fingerprinting and functional interrogation of natural populations have become common, enabled by a range of molecular and bioinformatics techniques. Recent studies on the ecology of Cyanobacteria  have covered many habitats and have demonstrated that cyanobacterial communities tend to be habitat-specific and that much genetic diversity is concealed among morphologically simple types.  Molecular, bioinformatics, physiological and geochemical techniques have combined in the study of natural communities of these bacteria.