Lecture 13 Flashcards
HD
Most interactions between microbes and animals are ___________.
beneficial
The mutualistic relationships of microbial and animal populations involve _____ and _______
nutrient exchange and maintenance of a suitable habitat.
Internal mutualistic associations of microbes with ruminants help animals to digest difficult components of their diet, particularly _________.
cellulose
Many invertebrate animals can satisfy part or all of their food requirements by preying on microorganisms _____ _____ times smaller in biomass than themselves
10 to th 5 - 10 to the 7
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
Grazing on microbial aggregations
Filter feeding
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.
scrape and ingest
When the predator pursues coherent masses of millions of microbes rather than individual prey it is called
grazing
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.
coprophagous
Dung loving bacteria
Rhodococcus coprophilus
Benthic invertebrates: permanently attached underwater planktonic invertebrates: float and move in the water column both exhibit _________ ________ strategy to exploit suspended planktonic microbial prey.
filter-feeding
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 ________ _______.
cilia, mucous nets
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.
mutualistic
Various leaf-cutting ant populations maintain mutualistic relationships with _______
fungi
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.
cellulase enzymes, anaerobic, 30-40C, 5.5-7.0
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
FYI
Organic acids are absorbed into the blood stream of the animal, where they are oxidized aerobically to produce ________
energy.
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.
protein
Bacterial populations within the rumen include
Cellulose, starch and hemicellulose digesters, Sugar fermenters, Fatty acid utilizers, Methanogenic bacteria, Proteolytic bacteria and lipolytic bacteria
The formation of methane, methanogenesis, is predominantly a microbial process, although a small amount of methane is generated naturally through ______ _______
volcanic activity
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.
anaerobic
The organisms responsible for methanogenesis are a group of obligately anaerobic archeabacteria called the ___________
methanogens
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
rhizosphere
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.
rhizosphere
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.
commensal and mutualistic
Microorganisms also inhabit the root itself and they are known as ________.
endophytes.
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
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
Within the rhizosphere, plant roots have direct influence on the composition and density of the soil microbial population known as the _______ ________
rhizosphere effect.
Some of the bacteria in the rhizosphere using the root exudates as an energy source to fix the_________
nitrogen.
Organic materials released from roots include
amino acids keto acids vitamins sugars tannins alkaloids phosphatides
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.
FYI
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.
mycorrhizae
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
morphological units
There are two basic types of mycorrhizal associations:
ectomycorrhizae (outside)endomycorrhizae (inside)
In some cases endo- and ectomycorrhizae may be combined, and are referred to as an
ectendomycorrhizae.
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.
ectomycorrhizae
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.
Endomycorrhizae
There are three main types of endomycorrhiza:
a) vesicular-arbuscular (VA) type
b) The ericoid type
c) The orchid type
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
FYI
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 _______.
nodule.
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.
ammonia
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 ___________
Rhizothamnion.
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).
FYI
Stems, leaves and fruits of plants provide suitable habitats for microbial populations called _____ _______
epiphytic microorganisms
The habitat adjacent to the plant surface is known as the _________, and the habitat directly on the surface of the leaf is the _________.
phyllosphere, phylloplane
The numbers of microorganisms on leaf surface depends on what 2 things?
on the season and the age of the leaf.
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.
FYI
Epiphytic microorganisms also exhibit various ______ _______ mechanisms that allow them to move from one plant surface to another.
spore discharge
Insects play an important role in the dissemination of microorganisms on fruit surfaces. Fruit flies carry _______ between fruit surfaces.
yeasts
Sometimes there is a close synergistic relationship among microorganisms, insects and plants figs+yeasts+fig wasps.
FYI
