MICROBIOLOGY

TYPES OF ASSOCIATION: Ignoring a low rate of mutation as a source of heterogeneity, bacterial division results in clonal  expansion, with the daughter cells considered to be similar if not identical to the parent cells.  Collectively, these cells are called a population. However, bacteria rarely exist as a single species  within any one habitat but, instead, are usually found as collections of different species called  communities, where each particular species will exist in a particular niche but may well contribute to  the maintenance of the entire community (e.g. syntrophism).  Interactions between microbial communities may have a negative (e.g. competition) or positive (cooperation) outcome. The interactions will be between both a single population (i.e. between members of  the same species) or between members of different populations. Typically, co-operation will occur at  low population densities, whereas competition will dominate at high population density

MICROBIAL WHOLE-CELL BIOREPORTERS: Over a quarter-century ago,luminescent bacteria were introduced as bio-sensors for the rapid assessment of toxic compounds in aquatic environments. The use of these organisms has now become “institutionalized” for a wide range of toxicological assays. These assays are versatile because the change in signal (bio luminescence) is linked directly to change in the global metabolism of the cell independent of the cause. The advent of genetic manipulation by recombinant DNA technology has created a broad range of specific microbial bio-sensors. The great majority of these are genetically engineered bacteria within which a promoter–operator (the sensing element) responds to the stress condition (toxic organic or inorganic compound, DNA damage, etc.) and changes the level of expression of a reporter gene that codes for a protein (the signal). The protein may be detected either directly (e.g., green fluorescent protein) or through  its catalytic ac

ENVIRONMENTAL APPLICATIONS OF MICROORGANISMS : 3)  BIOMINING: HEAVY METAL EXTRACTION  USING MICROORGANISMS:    Biomining utilizes naturally occurring prokaryotic communities. Here, microorganisms are used to leach metals, principally copper but also nickel  and zinc, from low-grade sulfide- and/or iron-containing ores. The process exploits the energy metabolism of various acidophilic chemolithoautotrophs that utilize inorganic compounds as energy sources and carbon dioxide as the source of carbon. These organisms use either ferrous iron or sulfide as an electron donor and oxygen as an electron acceptor with the formation of ferric iron or sulfuric acid. In the first case, the subsequent reaction of Ferric ions with insoluble metal sulfides yields soluble metal sulfates; in the second, metal sulfides are oxidized directly to metal sulfates. The metals are readily recovered from the leachate by electrolytic procedures, and the residual solution is recycled. Gold is inert to m

ENVIRONMENTAL APPLICATIONS OF MICROORGANISMS: 2) BIO REMEDIATION:  Bioremediation depends on the activities of living organisms to clean up  pollutants dispersed in the environment. Physical or chemical treatments, such as vaporization, extraction, or adsorption, relocate rather than remove pollutants. In contrast, there are many instances in which biodegradation converts organic pollutants to harmless inorganic products, including carbon  dioxide, water, and halide ions. Other advantages are that bioremediation is generally inexpensive and causes little disturbance to the environment.  Naturally occurring consortia, frequently dominated by bacteria, have the  capacity to degrade a wide spectrum of environmental pollutants.    Notably, such consortia are responsible for the cleanup of massive oil  spills. There is a long list of oil spills with serious environmental impact.  Following are three of many examples of this type of widely dispersed pollution. In March 1989, some 41 mi