Microbiology of Soils
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Which
of the following is capable of oxidizing sulfur to sulfates?
a. Thiobacillus thiooxidans
b. Desulfotomaculum
c. Rhodospirillum
d. Rhodomicrobium
Most
soil protozoa are flagellates or amoebas, having their dominant mode of nitrogen
as _____________.
a. ingestion of bacteria
b. ingestion
of mold
c. ingestion
of fungi
d. all
of these
Which
of the following microorganism use H2S as the electron donor to reduce carbon
dioxide?
a. Chromaticum
b. Chlorobium
c. Both (a) and (b)
d. Rhodomicrobium
Nitrifying
bacteria can not be isolated directly by the usual techniques employed to
isolate hetrotrophic bacteria. The reasons may be due to _____________.
a. slow growth
b. medium
growth
c. fast
growth
d. none
of these
The
nonsymbiotic bacteria which fix nitrogen live in the soil independently are _____________.
a. Azotobacter
b. Clostridium
c. considerably
less important in comparison to the symbiotic bacteria
d. all of the above
Nitrogen
fixation by the microorganisms can be detected by adopting the approach of _____________.
a. demonstrating
growth in a nitrogen free medium
b. cultivating
the microorganisms in the presence of nitrogen labeled with isotropic nitrogen
c. measuring15N2
by mass spectrometer
d. all of the above
Which
of the following is not the biofertilisers producing bacteria?
a. Nostoc
b. Anabaena
c. Both
(a) and (b)
d. Clostridium
The
population of algae in soil is __________ that of either bacteria or fungi.
a. generally smaller than
b. generally
greater than
c. equal
to
d. none
of these
The
transformation of nitrates to gaseous nitrogen is accomplished by
microorganisms in a series of biochemical reactions. The process is known as _____________.
a. nitrification
b. denitrification
c. nitrogen
fixation
d. ammonification
Nitrogen
fixation refers to the direct conversion of atmospheric nitrogen gas into _____________.
a. ammonia
b. glucose
c. ATP
d. nitrate
The
diagnostic enzyme for denitrification is _____________.
a. nitrate reductase
b. nitrate
oxidase
c. nitro
oxidoreductase
d. none
of these
A
heterocyst is _____________.
a. a
type of spore
b. a terminally differentiated cell that
fixes nitrogen
c. the
progenitor of cyanobacterial vegetative cells
d. a
cell that carries out oxygenic photosynthesis
Bacteria,
as a group, are responsible for _____________.
a. nitrogen
oxidation
b. sulfur
oxidation
c. nitrogen
fixation
d. all of these
The
phenomenon of commensalism refers to a relationship between organisms in which _____________.
a. one species of a pair benefits
b. both
the species of a pair benefit
c. one
species of a pair is more benefited
d. none
of the above
An
example of a symbiotic nitrogen fixer is _____________.
a. Azotobacter
b. Beijerinckia
c. Clostridium
d. Rhizobium
Which
of the following is correct?
a. Mycorrhizae
are fungi that form a mutually beneficial (symbiotic) relationship with plant
roots
b. The
fungi aid in transmitting nutrients and water to the plant roots
c. The
increased nutrient availability from mycorrhizae is thought to be due to the
additional absorbing surface provided by the fungi
d. All of the above
In
the process of nitrogen fixation, which of the following microorganism is
involved?
a. Non
symbiotic microorganisms only
b. Symbiotic
microorganisms only
c. Non symbiotic and symbiotic microorganisms
only
d. None
of the above
The
groups of symbiotic bacteria, which have the ability to fix nitrogen _____________.
a. derive
their food and minerals from the legume, and in turn they supply the legume
with some or all of its nitrogen
b. grow
together for a mutual benefit is called symbiosis and so these bacteria are
called symbiotic nitrogen-fixing bacteria
c. these
bacteria are from the genus, Rhizobium
d. all of the above
Nitrogen
oxidation (nitrification)refers to the _____________.
a. conversion of ammonium ions into nitrates
through the activities of certain bacteria.
b. changing
of atmospheric nitrogen (N2) to nitrogen compounds
c. sulfur
is oxidized to the sulfate form through Thiobacillus bacteria
d. none
of the above
Which
of the following statement is not true about composition of biogas?
a. It
is composed almost exclusively of methane and carbon dioxide
b. It
also contains with traces of H2S, N2, H2and CO
c. It also contains with traces of O2 and Cl2
d. Both
(a) and (b)
The
physical structure of soil is improved by the accumulation of _____________.
a. mold mycelium
b. minerals
c. water
d. all
of these
_____________
play a key role in the transformation of rock to soil.
a. Cyanobacteia
b. Pectin
decomposing bacteria
c. Nitrifying
bacteria