BIOL 2070 Chapter 5: Microbiology Topic 5

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orangehorse801

7 Feb 2017

School

University of Windsor

Department

Biological Sciences

Course

BIOL 2070

Professor

tanyanoel

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All living organisms eat, or at least they have nutritional needs. This is true for growing plants, cultivating livestock, and when we grow bacteria, they need to be fed as well. There is a diversity of nutritional strategy and capabilities of microbes. Depending on the organism, the carbon and the energy source will vary, as will the conditions under which they can grow. Culture media must provide necessary nutrients for microbes we want to culture. Common ways we grow microbes: broth (liquid) medium: tubes, flasks, solid medium (includes agar): petri dishes, test tubes (slants) If we want to keep microbes alive in the lab, we need to provide them with appropriate nutrients and conditions. We use culture (or growth) medium to supply most, if not all, of the nutrient s. Sometimes we grow bacteria in liquid media; other times we use solid media, which would be slants in a test tube or agar plates.

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When a soil dries out, this has a negative impact on the activity of soil bacteria. Using an innovative combination of state-of-the-art analysis and imaging techniques, researchers at UFZ have now discovered that fungi increase the activity of bacteria in dry and nutrient-poor habitats by supplying them with water and nutrients. The ability of fungi to regulate drought stress in soil and thus sustain ecosystem functions is an important insight in the context of climate change.

Many fungi spread through the soil with a fine network of thin filaments known as hyphae. In their search for water and nutrients the hyphae grow in different directions, constantly enlarging the network. Once found, water and nutrients are absorbed and transported through the hyphae, allowing them to be supplied to parts of the fungal network in dry or nutrient-poor areas of the soil. But it isn't only the fungus itself which benefits from the transport of material through the hyphal pipelines: bacteria, too, are kept supplied with the water and nutrients they need to thrive. This has now been demonstrated by a team of UFZ researchers in a study recently published in the journal Nature Communications. "We've suspected for a long time that fungi play an important role in the soil moisture budget," says UFZ environmental biotechnologist Prof. Matthias KÃ¤stner. "Now, using secondary ion mass spectrometry techniques (NanoSIMS and ToF-SIMS) from the ProVIS research platform at UFZ, we've finally obtained experimental evidence."

As part of their investigations, the researchers closely examined the transport of water, substrates and nutrients through the microscopically small hyphae of fungi. They grew the fungi on a culture medium of water, glucose and nitrogen-containing nutrients. The fungal hyphae had to pass through a dry, nutrient-free zone in order to grow through into a new area containing the culture medium. The inhospitable transition zone contained spores of the common soil bacterium Bacillus subtilis. Spores are inactive stages of Bacillus that form when there is insufficient water, food and nutrients available for bacterial growth. The bacteria go into a kind of dormant stage, from which they only awake once the environmental conditions are more favourable for living again.

In the experiment, these conditions were indeed improved by the growth of the fungi: "As the fungal hyphae grew through the dry zone, the bacterial spores germinated and we noticed clear microbial activity," says UFZ environmental microbiologist Dr. Lukas Y. Wick. "The fungi obviously improved the environmental conditions for the bacteria and woke them from their slumber, like Sleeping Beauty." But what exactly happens at a chemical level when fungal hyphae grow in direct proximity to bacterial spores? To answer this question, the researchers 'labelled' the water, glucose and nitrogen-containing nutrients in the culture medium in advance with stable isotopes. If these substances were transferred from the fungus to the bacteria, they could be detected using the isotopic marker and the NanoSIMS method, with nano-scale spatial resolution. "The NanoSIMS method reveals the distribution of elements and isotops and therefore allows us to observe metabolic processes," KÃ¤stner explains. "As it turns out, we did find the stable isotopes of the labelled water, glucose and nitrogen-containing nutrients in the cell mass of the bacteria -- which could only have come from the fungi."

This study has given the UFZ researchers another important insight into fungi and their important function in soils. Fungi serve as pumping stations and pipelines for water, substrates and nutrients and can colonise inhospitable locations, making them habitable for bacteria -- and thus stimulate microbial activity in the soil. In previous work the researchers have already shown that fungal hyphae act as a kind of fungal highway for bacteria, allowing them to move around, and provide a hotspot for bacterial gene transfer. Wick continues: "The results of this latest study demonstrate once again that, through their interaction with bacteria, fungi play a significant, previously underestimated role in the soil ecosystem."

If a soil is contaminated with pollutants, for example, bacteria can break them down. But if the soil is too dry, the degradation processes will come to a standstill. "If the drought period lasts for a limited time, fungi have a stabilising effect and can keep soil processes going. This could be important specifically with regard to the impacts of climate change, if the ratio of dry to moist areas of soil dramatically increases," says KÃ¤stner. In future investigations, the researchers therefore intend to look even more closely at soil as a true ecosystem. "We want to carry out soil experiments under different environmental conditions and find out what influence fungal growth has on the breakdown of pollutants," says Wick. He adds: "It's important to have a better understanding of the role of fungi in the soil ecosystem. Only when we know how soil works can we respond to changes, for example those caused by climate change, with informed decisions."

Question 1

A microorganism's ability to use a harmful pesticide as a source of carbon and energy is an example of

Select one:

a. chemoautotrophy

b. nitrogen fixation

c. bioremediation

d. photoautotrophy

e. biosynthesis

Question 2

Autotrophs and heterotrophs differ in

Select one:

a. their ability to utilize CO2 as a sole carbon source.

b. their ability to incorporate CO2 into cells.

c. only a few enzymes.

d. their ability to synthesize precursor molecules.

e. their ability to utilize CO2 as a sole energy source.

Question 3

If the amino acid valine constituted approximately 4% of the total cell protein of a bacterium, how much valine should be added to a defined medium in order to grow 1 gram of this organism?

Select one:

a. 0.2 mg

b. 2 mg

c. 20 mg

d. 40 mg

e. 200 mg

Question 4

Transport of HPO₄ along with a proton (H⁺) is an example of

Select one:

a. antiport

b. uniport

c. facilitated diffusion

d. symport

e. group translocation

Question 5

The energy required for transport via ABC transporters is derived from

Select one:

a. a proton gradient

b. an electrical charge separation across the membrane

c. ATP hydrolysis

d. a symport mechanism

e. a high energy phosphate bond of PEP

Question 6

The spread plate method would clearly be preferred over the pour plate method when isolating colonies of

Select one:

a. anaerobic bacteria

b. thermophilic bacteria

c. bacteria from temperate lake zones

d. purple non-sulfur bacteria

e. agar-degrading bacteria

Question 7

Enrichment culture procedures for many microorganisms require intial growth in liquid media, followed by growth on solid media. The solid media is used to

Select one:

a. provide proper growth conditions.

b. isolate single colonies of the microbes.

c. get rid of competing microorganisms.

d. isolate strict aerobes.

e. enrich for specific nutrients.

Question 8

The optical density of light scattered by bacteria is a very useful tool for estimating population size. What can alter the bacteria's light-scattering properties?

Select one:

a. Cell volume depending on its growth stage

b. The condition of being absent of microorganisms.

c. The amount of light projected from the room.

d. The standard curve

e. Standard deviation from growth curve.

Question 9

What is true about a bacterial colony?

Select one:

a. It arises from an individual cell and represents an isolate strain.

b. Colonies, and CFU (colony forming units) on streak plates represent a diverse microbial culture.

c. In order to obtain a colony, on must perform cloning steps.

d. Axenic cultures to not represent CFUs or colonies.

e. Colonies require differential media in order to separate them from the population.

Question 10

What is a biofilm?

Select one:

a. All cells in a population achieve a steady state

b. A specialized, surface-attached, collaborative community of bacteria

c. A complex media made of the chemical building blocks that a cell needs

d. A type of anaerobic growth chamber.

e. A type of spore

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BIOL 2070 Chapter 5: Microbiology Topic 5

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