Microbiology Exam 3 Practice (HW and quiz)
If the biochemical oxygen demand (BOD) of a lake is very high, how will that affect the aquatic life in the lake?
There will be less oxygen available for the aquatic life due to the microbial activity.
Why would using nitrogenous fertilizer near a body of water affect the organisms in the body of water?
When runoff enters the body of water, the nitrogen level significantly increases, which increases the activity of the microorganism there and upsets the balance of the ecosystem.
Greenhouse gases
such as CO2, CH4, and N2O trap infrared radiation and heat the Earth.
A soil clump has an oxic (oxygen containing) zone containing aerobic and facultatively aerobic organotrophs, and an anoxic zone containing fermentative bacteria, sulfate reducers, and denitrifyers. This soil clump has at least __________ different habitats, __________ different communities and __________ different guilds
2,2,5
Decomposition of organic carbon ultimately results in the formation of __________.
CO2 in aerobic environments and CO2 plus CH4 in anoxic environments
Ferrous iron (Fe2+) oxidation generally occurs in environments with
High H+ concentrations
A small farm pond containing many species of microorganisms (bacteria, cyanobacteria, algae, and protozoa) was perturbed when runoff from a manure pile entered the pond. The added nutrients soon turned the water green due to a bloom of cyanobacteria. How did this affect the microbial community in the pond?
Species richness decreased and species abundance increased.
How do arbuscular mycorrhizae (AM) help plants obtain more nutrients from the soil?
The AM increase the total surface area to absorb more nutrients
Which statement is TRUE about the fluid from the hydrothermal vents?
The fluid contains large amounts of reduced inorganic materials.
Nitrogen fixation results in the
addition of biologically available N to an ecosystem.
What metabolism would be favored when there is a lack of electron acceptors?
anaerobic fermentation
Microbial mats differ from biofilms in that they __________.
are currently found only in extreme habitats
Nitrifying Thaumarchaeota outcompete nitrifying bacteria in many aquatic and terrestrial environments because Thaumarchaeota
are well-adapted to very low nutrient and electron donor concentrations.
Anoxygenic phototrophs
can be either autotrophic or heterotrophic and may use a variety of electron donors for photosynthesis.
From the aquatic systems below, where are heterotrophic Bacteria the MOST abundant?
coastal waters
Mutualisms may become prolonged, intimate and obligate symbioses through the process of __________.
coevolution
Microbes that have a mutualistic relationship with their host are beneficial to their host, while __________.
commensals have little or no effect on the host
The fate of carbon fixed by primary producers such as phytoplankton occurs by all EXCEPT: A) Consumption by zooplankton grazers B) Consumption by other phytoplankton C) Consumption by heterotrophic bacteria D) Processed by viruses
consumption by other phytoplankton
In which of the following environments would you expect to find a high number of iron-reducing bacteria?
deep subsurface
The methodology of microbial ecology includes
enrichment and isolation of specific microbes, cell-staining, and gene, transcript, and protein characterization.
In anoxic environments, organic compounds are cycled back to carbon dioxide and methane by __________.
fermentation
For microbial biodiversity studies, it is common to identify the ________ rather than the ________ as a measure of biodiversity.
genes/ organisms themselves
Culture-independent approaches avoid issues associated with
growing organisms in the lab
The science of microbial ecology deals with
how the activity and biodiversity of microbial communities affect microbial interactions with each other and the environment.
The phylogenetic analysis of complex microbial communities often targets small subunit (SSU) ribosomal RNA genes. This is because rRNA is found in all organisms and __________.
is highly conserved over evolutionary time
Bacteria will become part of a biofilm because __________.
it allows them to remain in a favorable niche
Most marine Bacteria are thought to be chemoorganotrophs. Given the extremely low concentrations of nutrients in the open ocean, they typically need all of the following adaptations EXCEPT __________.
large cell size
Bacterial oxidation of Fe2+ occurs BEST under which environmental condition?
low (acidic) pH
Based on comparative studies of agricultural soils or polluted soils compared with undisturbed soils, disturbance of soil microbial communities tends to lead to __________.
lower prokaryotic diversity
In Bacteria, the MOST common oxidized form of nitrogen is ________ and of sulfur is ________.
nitrate/sulfate
Which part of the nitrogen cycle increases the chances for nitrogen to get leached from soils into aquatic ecosystems?
nitrification (ammonium to nitrate)
Which of the following pairs of microorganisms are NOT likely to form close associations or consortia?
nitrogen-fixing cyanobacteria and dissimilative sulfate-reducers
Bacterial abundance (102 to 108) and generation times (days to centuries) vary by many orders of magnitude in the deep subsurface mainly due to __________.
nutrient limitations
Nitrification and anammox both
oxidize ammonia, but nitrification uses O2 and anammox uses NO2- for electron acceptors.
Microenvironments of soil exist where ________ concentrations greatly vary
oxygen, nitrate and sulfur
Dissimilatory sulfide-oxidizers use a variety of unique ecological strategies in order to
position themselves at interfaces where sulfide and oxygen meet
Two major environmental extremes of the deep sea are high ________ and low ________.
pressure/ nutrient levels
Diazotrophs maximize nitrogenase activity by
producing specialized structures or fixing N2 at times when oxygen is absent to protect nitrogenase from oxygen
The Fe and Mn cycles include
reduced and oxidized forms that are very chemically reactive.
Metagenomics involves the analysis of a microbial community by __________.
sampling and sequencing all of the genes in an environment
Microbial diversity in an ecosystem can be expressed as the number of different species present, which is termed
species richness
Some nitrifying prokaryotes carry out metabolic cooperation by a process known as
syntrophy
Industrial production of nitrogenous fertilizers from N2 now equals or exceeds the amount of nitrogen fixation carried out by microbes in the biosphere. The resulting increase in primary production is an example of the fact that __________.
the C and N cycles are closely coupled
One important difference between the C, N, and S cycles and the P, Ca, and Si cycles is that
the P, Ca, and Si cycles do NOT involve redox changes or gaseous forms that can alter Earth's atmospheric chemistry.
Lichens are a mutualistic association of a fungus and either an alga or a cyanobacterium in which
the fungus protects the photosynthetic partner from erosion
In mycorrhizal mutualisms between plants roots and fungi
the plant supplies carbohydrates to the fungus and the fungus supplies phosphorus and nitrogen to the plant.
A farmer wants to acidify his alkaline soils by adding elemental sulfur (S0), which will, under the right conditions, be oxidized to H2SO4 by chemolithotrophs. However, the weather report predicts heavy rains and possible localized flooding starting within in a few days and lasting for the next couple of weeks. Why should the farmer wait to apply the S0 to his fields until the soils are well-drained?
to avoid production of hydrogen sulfide (H2S) due to anoxia
Compared with pure cultures grown in the lab, microbes in nature usually experience a wider range of environmental conditions, more variation in conditions over time, and more contact with other organisms. Therefore, the same organism in nature will __________.
typically grow slower than in pure culture
Under what scenario would an oligotroph outcompete a copiotroph in the soil?
under low nutrient conditions
