Micro Exam 3 prep

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 dec. and species abundance inc.

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

The metabolic diversity of photosynthetic bacteria stems from different

light-harvesting complexes, electron donors, and organic compounds they produce

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

Metagenomics involves the analysis of a microbial community by __________.

sampling and sequencing all of the genes in an environment

Two major environmental extremes of the deep sea are high ________ and low ________.

pressure / nutrient levels

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 denitrifiers. 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

Chemical reactions involving ____ have been proposed as energy-yielding reactions for primitive organisms.

S and H2

All of the following are true to biofilms

biofilms protect organisms from antibiotics biofilms form on virtually all submerged surfaces in nature biofilms formation and dispersal are regulated processes

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.

Nitrogen fixation results in the

addition of biologically available nitrogen to an ecosystem

Microbial mats differ from biofilms in that they __________.

are currently found only in extreme habitats

From the aquatic systems below, where are heterotrophic Bacteria the MOST abundant?

coastal waters

A species of insect that lives solely on pine sap was found to contain a bacterial symbiont. Genome sequencing of both the host and the symbiont revealed that the symbiont lacked many genes required for energy production, and the host lacked genes for biosynthesis of several essential amino acids. what is/are the most likely mechanisms that caused the loss of these genes?

coevolution

Mutualisms may become prolonged, intimate and obligate symbioses through the process of __________.

coevolution

the fate of carbon fixed by primary producers such as phytoplankton occurs by all

consumption by zooplankton grazers consumption by heterotrophic bacteria processed by viruses

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, 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

Ferrous iron (Fe 2+) oxidation generally occurs in environments with

high H+ concentrations

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

Dissimilatory sulfide-oxidizers use a variety of unique ecological strategies in order to

position themselves at interfaces where sulfide and oxygen meet.

Two organisms that both benefit from each other are in a symbiotic relationship called

mutualism

which part of the nitrogen cycle increases the chances for nitrogen to get leached from soils into aquatic ecosystems

nitrification (ammonium to nitrate)

pair of microorganisms that are NOT likely to form close associations or consortia

nitrogen-fixing cyanobacteria and dissimilative sulfate-reducers

Bacterial abundance (10^2 to 10^8) 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 where ____ concentrations greatly vary.

oxygen, nitrate and sulfur

Microbial diversity in an ecosystem can be expressed as the number of different species present, which is termed

species richness

Greenhouse gases

such as CO2, CH4 and N2O trap infrared radiation and heat the Earth

Some nitrifying prokaryotes carry out metabolic cooperation by a process known as

syntrophy

How do arbuscular mycorrhizae (AM) help plants obtain more nutrients from the soil

the AM increase the total surface area to absorb more nutrients

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.

Which statement is TRUE about the fluid from the hydrothermal vents?

the fluid contains large amounts of reduced inorganic materials

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

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

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