Environmental problems – An overview - Environmental Deterioration and Contamination: Problems and their Management - page 15

Figure 1.10 Mineralization and humus formation in the soil.

is the first known form of life that not only tolerates high arsenic concentrations, but
also incorporates arsenic into its cells to substitute phosphorous (Wolfe-Simon, 2011).
Later on Erb et al. (2012) disproved a former misstatement, saying that “GFAJ-1
is able to grow at low phosphate concentrations (1.7

µ

M), even in the presence of
high concentrations of arsenate (40 mM), but lacks the ability to grow in phosphorus-
depleted ( < 0.3

M), arsenate-containing medium.'' Their chemical analyses confirmed
the presence of normal phosphorous-containing DNA in the cells of the extreme living
bacterial species.
The enzymes and genes of these extreme-living microorganisms may have sig-
nificant importance in modern biotechnologies and benefit for the industries based
on them. We could mention the enzymes from heat resistant species, such as proteases
and lipases added to laundry detergents or the thermostable DNA polymerase from the
bacterium of Thermus aquaticus . This is the reason for the vogue of microbe-hunting
amongst researchers.
From the extreme microorganisms let us return now to the role of microbes in
mineralization in the soil which is the most common step of the life cycle of biogenic
elements and the most important role of soil microbiota.
Figure 1.10 summarizes all mineralization and humus forming processes in the soil
and the role of soil microorganisms in the complex process.
Dead organic matter (straw, fall litter) on the soil is gradually degraded into smaller
and smaller pieces by worms, insects and filamentous fungi, also bacteria participate in

µ