Exam 29: Microorganisms in Terrestrial Ecosystems

Oxygen diffuses through water approximately 4,000 times faster than through dry soil.

Recent studies indicate that active prokaryotic assemblages are present in high-temperature oil reservoirs, including such genera as

In the shallow subsurface, surface waters often move through ________, which are porous geological structures below the plant root zone.

The surface of a plant root is called the __________.

Except for a shallow surface layer, the earth's crust is known to be free of microorganisms.

The plant leaf surface is called the rhizosphere.

Legume plants provide certain amino acids to the ___________ so that they do not need to assimilate ___________. In return, the bacteroids shuttle amino acids bearing the fixed nitrogen back to the plant.

Most ectomycorrhizae produce signaling molecules that limit the growth of root hairs.

A mineral soil contains less than 20 percent organic carbon while an organic soil contains at least that amount.

One of the most common bacterial genera cultured from plant leaves is

Fungi can be present at up to several hundred meters of hyphae per gram of soil.

Mycorrhizal fungi can either be intracellular or extracellular.

Most organic matter found in soils results from primary producers such as

Protozoa in soils utilize bacteria as a nutrient source.

An important bacterial mediated process that occurs on the surface of plant roots is called _________ nitrogen fixation.

The vast majority of microorganisms found in soils have been successfully cultured in the laboratory.

A common resident of the rhizosphere that can enhance plant growth is

Lignin degradation by basidiomycetes is an aerobic process that is catalyzed by phenoloxidases.

Which of the following statements is correct?

A substance that promotes binding of Rhizobium to plant root hairs is called a __________ factor.