Chapter 23. Major Microbial Habitats And Diversity

Front 1

Parasitism

Back 1

one member in the relationship is harmed and the other benefits

Front 2

Mutualism

Back 2

both species benefit

Front 3

Commensalism

Back 3

one species benefits and the other is neither harmed nor helped

Front 4

Ecosystem

Back 4

the sum total of all organisms and abiotic factors in a particular environment interacting as a system

Front 5

Habitat

Back 5

portion of an ecosystem where a community could reside

Front 6

What is the difference between species richness and species abundance?

Back 6

Species richness is the total number of different species present whereas species abundance is the proportion of each species in an ecosystem

Front 7

How do most microorganisms deal with the “feast-or-famine” situation?

Back 7

Make storage polymers

Front 8

Explain why growth rates of microbes in nature are usually well below maximum growth rates seen in the laboratory?

Back 8

Resources and growth conditions are suboptimal, distribution of nutrients is not uniform and competition and cooperation occurs here.

Front 9

The surface of a rock in a flowing stream will often contain a biofilm. What advantages could be conferred on bacteria growing in a biofilm compared with growth within the flowing stream (free-floating)?

Back 9

Trap nutrients for microbial growth and helps prevent detachment of cells in flowing systems.

Front 10

What are biofilms? Describe the process of biofilm formation

Back 10

Biofilms are assemblages of bacterial cells adhered to a surface and enclosed in an adhesive matrix excreted by the cells. The matrix is a mixture of polysaccharides, proteins and nucleic acids. Biofilm formation is initiated by attachment of a cell to a surface followed by expression of biofilm-specific genes. Genes encode proteins that synthesize intercellular signaling molecules and initiate matrix formation.

Front 11

Biofilms have significant implications in human medicine and commerce. Discuss.

Back 11

Biofilms have been implicated in several medical and dental conditions (periodontal disease, kidney stones, tuberculosis, Legionnaires’ disease, and Staphylococcus infections). Periodontal disease is a Infection of tissues surrounding and supporting the teeth; key cause of tooth loss in older adults

Front 12

What is a microbial mat?

Back 12

Very thick biofilms built by phototrophic and/or chemolithotrophic bacteria.

Front 13

In what soil horizon are microbial numbers and activities the highest, and why?

Back 13

A horizon. Surface soil (high in organic matter, dark in color, is tilled for agriculture)

Front 14

List one way of determining soil prokaryotic diversity that does not involve actual culturing or growing of organisms from environmental samples.

Back 14

Phylogenetic sampling

Front 15

In a freshwater lake, where is the epilimnion and where is the hypolimnion? Explain the term fall turnover- with reference to a lake and how it affects the microbial communities in these waters.

Back 15

Epilimnion is found in less dense surface water whereas the hypolimnion is in the colder, denser, bottom layer. Microbial activity and community composition is altered with changes in oxygen content, but other factors that accompany fall turnover of the water column, especially changes in temperature and nutrient levels, govern microbial diversity and activity as well.

Front 16

How do microbial numbers in open ocean waters compare to those in fresh water ecosystems? Explain a reason for this observation.

Back 16

Compared with most freshwater environments, the open ocean environment is saline, low in nutrients (especially with respect to nitrogen, phosphorus, and iron), cooler. Due to the size of the oceans, the microbial activities taking place in them are major factors in Earth’s carbon balance.

Front 17

Name the most abundant oxygenic phototroph found in the ocean.

Back 17

Trichodesmium

Front 18

In the open ocean, ____ (bacteria/archaea) dominate waters above 1000m.

Back 18

Bacteria

Front 19

Piezophiles

Back 19

An organism that lives optimally at high hydrostatic pressure

Front 20

Extreme piezophiles

Back 20

A piezophilic organism unable to grow at a pressure of 1 atm and typically requiring several hundred atmospheres of pressure for growth

Front 21

Piezotolerant

Back 21

An organism able to tolerate high hydrostatic pressure but growing best at 1 atm.

Front 22

How does a warm hydrothermal vent differ from a black smoker, both chemcially and physically?

Back 22

Warm, diffuse fluids are emitted from cracks in the seafloor and the exterior walls of hydrothermal chimneys. The fluids originate from the mixing of cold seawater with hot hydrothermal fluids in subsurface regions of the sediments. Hot vents, called black smoker, form upright sulfide edifices called chimneys that be less than 1 m to over 30 m in height. Chimneys form when acidic hydrothermal fluids rich in dissolved metals and magmatic gases are suddenly mixed with cold, oxygenated seawater.

Front 23

Why are chemolithotrophic bacteria so prevalent at hydrothermal vents?

Back 23

Sulfidic vents support sulfur bacteria, whereas vents that emit other inorganic electron donors support nitrifying, hydrogen-oxidizing, iron- and manganese-oxidizing, or methylotrophic bacteria, the latter presumably growing on the CH4 and carbon monoxide (CO) emitted from the vents