Environmental problems – An overview - Environmental Deterioration and Contamination: Problems and their Management - page 12

mobile genetic elements, plasmids). The genetic information and the size of the
metagenome (the sum of DNA and the genes of the species of the ecosystem) and
its dispersion rate are gradually growing. The species and the communities are
capable of tolerating increasing deviation of environmental parameters and the
ecosystem becomes more and more tolerant and resistant.
Microorganisms play a major role in energy and element cycles and the regulation
of the processes (Figure 1.7).
Nitrogen and sulfur cycling is highly dependent on microbial potential and activ-
ity. Figures 1.8 and 1.9 introduce the role of microbes in addition to the main
transformation routes and redox conditions (aerobic-anaerobic). The scheme shows
that microorganisms are able to utilize any form of N and S for energy produc-
tion or biosynthesis. There are similar pictures for any of the element cycles in the
ecosystem.
Human activities, anthropogenic emission into the environment, additional mass
to cycling elements (CO 2 , CO and CH 4 , from industrial and agricultural production,
NO x and SO x from fossil energy sources, S from bioleaching of sulfide minerals), stress
by contaminants (toxic metals, organic contaminants), selective deterioration of the
sensitive species increase the intensity and speed of natural trends and result in an
imbalance, which—very probably—cannot be neutralized by the ecosystem itself, and
as an unpredictable consequence may terminate the current homeostasis.
As one could understand from the list of the global ecological trends, the role of
microorganisms is significant in mineralization and biosynthesis and in maintaining
Figure 1.7 Microbial processes in energy and carbon cycling.