Lecture 13

Question 1

Most interactions between microbes and animals are ___________.

Answer 1

beneficial

Question 2

The mutualistic relationships of microbial and animal populations involve _____ and _______

Answer 2

nutrient exchange and maintenance of a suitable habitat.

Question 3

Internal mutualistic associations of microbes with ruminants help animals to digest difficult components of their diet, particularly _________.

Answer 3

cellulose

Question 4

Many invertebrate animals can satisfy part or all of their food requirements by preying on microorganisms _____ _____ times smaller in biomass than themselves

Answer 4

10 to th 5 - 10 to the 7

Question 5

Many invertebrate animals can satisfy part or all of their food requirements by preying on microorganisms greatly smaller in biomass than themselves. They use what two feeding strategies

Answer 5

Grazing on microbial aggregations 

Filter feeding

Question 6

A common feeding strategy of aquatic Gastropoda (snails), Echinodermata (sea urchins), and Patellidae (limpets), is to _______ and _______ the microbial crust from submerged surfaces where the microbial populations are able to reach high densities because of the physical absorption of dissolved nutrients on these surfaces.

Answer 6

scrape and ingest

Question 7

When the predator pursues coherent masses of millions of microbes rather than individual prey it is called

Answer 7

grazing

Question 8

In the terrestrial environment, various soil microarthropods and certain rodents and lagomorphs, including rabbits, are _________ (grows on dung) and regularly reingest some of their own fecal material.

Answer 8

coprophagous

Question 9

Dung loving bacteria

Answer 9

Rhodococcus coprophilus

Question 10

Benthic invertebrates: permanently attached underwater planktonic invertebrates: float and move in the water column both exhibit _________ ________ strategy to exploit suspended planktonic microbial prey.

Answer 10

filter-feeding

Question 11

The animals remain more or less stationary and filter the prey out of suspension. This is an energetically advantageous strategy because the prey are minute and in a relatively homogenous suspension. The animals maintain a flow of water using _____ and/or various modified organs (legs, antennae, tentacles, gills, tails). Microorganisms are filtered through these organs and ________ _______.

Answer 11

cilia, mucous nets

Question 12

Several plant-eating insects cultivate pure cultures of microorganisms on plant tissues in a _________ relationship. The protein-rich microbial biomass is used as the principal food source by the insect population. In turn, the microorganisms are dispersed by the insects and are provided with a habitat in which they can proliferate.

Answer 12

mutualistic

Question 13

Various leaf-cutting ant populations maintain mutualistic relationships with _______

Answer 13

fungi

Question 14

Ruminant organisms do not produce ________ ________ themselves but depend on associated microbial populations for degrading cellulosic materials. The rumen provides a relatively uniform and stable environment that is ________, is _______ºC and has a pH of _________. These conditions, optimal for the associated microorganisms and the continuous supply of ingested
plant material permit the development of very dense communities of microorganisms.

Answer 14

cellulase enzymes, anaerobic, 30-40C, 5.5-7.0

Question 15

Microorganisms within the rumen convert cellulose, starch, and other ingested nutrients to carbon dioxide, hydrogen gas and methane, and low molecular weight organic acids such as acetic, propionic and butyric acids

Answer 15

FYI

Question 16

Organic acids are absorbed into the blood stream of the animal, where they are oxidized aerobically to produce ________

Answer 16

energy.

Question 17

Ruminants are also able to use the ________ produced by the associated microbial populations. Fermentatively produced CO2 and methane produced by methanogenic bacteria within rumen are expelled and do not contribute to the nutrition of the animal.

Answer 17

protein

Question 18

Bacterial populations within the rumen include

Answer 18

Cellulose, starch and hemicellulose digesters,  Sugar fermenters,  Fatty acid utilizers,  Methanogenic bacteria,  Proteolytic bacteria and lipolytic bacteria

Question 19

The formation of methane, methanogenesis, is predominantly a microbial process, although a small amount of methane is generated naturally through ______ _______

Answer 19

volcanic activity

Question 20

Methanogenesis is an _________ process and occurs extensively in specialized environments including water-saturated areas such as wetlands and paddy fields, anaerobic niches in the soil, landfills, the rumen, and termite guts.

Answer 20

anaerobic

Question 21

The organisms responsible for methanogenesis are a group of obligately anaerobic archeabacteria called the ___________

Answer 21

methanogens

Question 22

There is a specialized zone of soil under the influence of plant roots. This is known as the __________ and is of special interest to soil microbiologists and plant pathologists because of enhanced microbial activity and specific plant-microbe interactions

Answer 22

rhizosphere

Question 23

An ecological niche which comprises the surface of plant roots (the rhizoplane) and that region of the surrounding soil where microbial populations are affected by the presence of roots.

Answer 23

rhizosphere

Question 24

Rhizosphere is a zone of _________ and _______ interactions between plants and microbes. Overall microbial populations within the soil-plant-microorganism system can affect plant growth in beneficial or detrimental ways.

Answer 24

commensal and mutualistic

Question 25

Microorganisms also inhabit the root itself and they are known as ________.

Answer 25

endophytes.

Question 26

The rhizosphere effect occurs almost as soon as a seed is planted, with the area of increased microbial activity. The interactions of plant roots and rhizosphere microorganisms are based largely on interactive modification of the soil environment by processes such as

Answer 26

Water uptake by the plant, 
Release of organic chemicals to the soil by the roots,  Microbial production of plant growth factors,  Microbially mediated availability of mineral nutrients

Question 27

Within the rhizosphere, plant roots have direct influence on the composition and density of the soil microbial population known as the _______ ________

Answer 27

rhizosphere effect.

Question 28

Some of the bacteria in the rhizosphere using the root exudates as an energy source to fix the_________

Answer 28

nitrogen.

Question 29

Organic materials released from roots include



Answer 29

amino acids  
keto acids  
vitamins  
sugars  
tannins  
alkaloids  
phosphatides

Question 30

Furthermore, in a submerged plant environment, plants are protected against the toxic effect of hydrogen sulfide by mutualistic association with microorganisms e.g. Beggiatoa in rice plants. This microaerophilic, catalase-negative, sulfide-oxidizing, filamentous bacterium benefits from the oxygen and catalase enzyme provided by the rice roots. In turn, it aids the rice plant by oxidizing the toxic hydrogen sulfide to harmless sulfur or sulfate.

Answer 30

FYI

Question 31

Some fungi enter into mutualistic relationship with roots called ________ (“fungus root”) in which the fungi actually become integrated into the physical structure of the roots. The fungus derives nutritional benefits from plant roots, contributes to plant nutrition, and does not cause plant disease.

Answer 31

mycorrhizae

Question 32

Mycorrhizal associations involve the integration of plant roots and fungal mycelia, forming ________ _______. Mycorrhizal associations exist for prolonged periods with the maintenance of a healthy physiological interaction between the plant and the fungus. Enhanced uptake of water and mineral nutrients, particularly phosphorus and nitrogen during the mycorrhizal associations enables plants to occupy habitats they otherwise could not

Answer 32

morphological units

Question 33

There are two basic types of mycorrhizal associations:

Answer 33

ectomycorrhizae (outside)endomycorrhizae (inside)

Question 34

In some cases endo- and ectomycorrhizae may be combined, and are referred to as an

Answer 34

ectendomycorrhizae.

Question 35

ectomycorrhizae or endomycorrhizae: 
the fungus (an ascomycete or basidiomycete) forms an external sheath more than 40mm thick and constituting up to 40% of the dry weight of the combined root-fungus structure.

Answer 35

ectomycorrhizae

Question 36

ectomycorrhizae or endomycorrhizae:
invade the living cells of the root, which become filled with mycelial clusters. So it does not encounter competition with other soil microorganisms.

Answer 36

Endomycorrhizae

Question 37

There are three main types of endomycorrhiza:

Answer 37

a) vesicular-arbuscular (VA) type
b) The ericoid type
c) The orchid type

Question 38

VA Mycorrhiza found in a wide range of plants in which fungal hyphae spread through the primary cortex of the roots and penetrate cortical cells. An arbuscule is formed and both intracellular and extracellular hyphae develop spherical, lipid-rich swellings called vesicles. VA mycorrhizae improve the uptake of nutrients particularly phosphate by the host plant. Mycorrhizal association is essential to the orchid, at least for germination and seedling growth. Orchid seeds are very small and have little or no food reserve, so nutrients must be supplied by an invading fungus for germination. In Europe, commercial pine tree farms inoculate tree seedlings with soils containing effective mycorrhizae. In Australia this is done for Eucalyptus trees

Answer 38

FYI

Question 39

One of the most important mutualistic relationships between microorganisms and plants involves the invasion of roots of suitable host plants by nitrogen fixing bacteria, resulting in formation of a tumor- like growth called a _______.

Answer 39

nodule.

Question 40

Within the nodule, the nitrogen-fixing bacteria are able to convert atmospheric nitrogen to _______, which supplies the nitrogen required for bacteria and plant growth. Nitrogen-fixing associations of rhizobia with leguminous plants are very important both in global nitrogen cycling and in agriculture.

Answer 40

ammonia

Question 41

Actinomycete called Frankia alni infects the roots of trees, leading to
the formation of nodule. Frankia species form associations with various non-leguminous plants including various woody shrubs and small trees. Frankia invades the meristem cells and the factors produced by this actinomycete stimulate the development of the roots. The division of the top meristem results in the formation of a cluster of lobes called ___________

Answer 41

Rhizothamnion.

Question 42

Crown gall is an extremely interesting plant disease that occurs after viable Agrobacterium tumefaciens cells enter through the root or wounded surfaces. The crown gall disease manifests itself in uncontrolled cell division in the host plant, which results in the formation of a tumor or gall typically around the crown of the root. However, the ability of this bacterium in invasion of plants is now being used for gene transfer (e.g. insecticide production by the plant).

Answer 42

FYI

Question 43

Stems, leaves and fruits of plants provide suitable habitats for microbial populations called _____ _______

Answer 43

epiphytic microorganisms

Question 44

The habitat adjacent to the plant surface is known as the _________, and the habitat directly on the surface of the leaf is the _________.

Answer 44

phyllosphere, phylloplane

Question 45

The numbers of microorganisms on leaf surface depends on what 2 things?

Answer 45

on the season and the age of the leaf.

Question 46

Epiphytic microorganisms on plant surfaces are directly exposed to climatic changes. These populations must withstand direct sunlight, periods of desiccation, and periods of high and low temperatures. Most successful epiphytes are pigmented and have specialized protective cell walls, adaptive features for withstanding these adverse environmental conditions.

Answer 46

FYI

Question 47

Epiphytic microorganisms also exhibit various ______ _______ mechanisms that allow them to move from one plant surface to another.

Answer 47

spore discharge

Question 48

Insects play an important role in the dissemination of microorganisms on fruit surfaces. Fruit flies carry _______ between fruit surfaces.

Answer 48

yeasts

Question 49

Sometimes there is a close synergistic relationship among microorganisms, insects and plants figs+yeasts+fig wasps.

Answer 49

FYI