HW 18 (microbio Exam 3)

Which approach would help to identify biologically produced sulfur in a sediment sample?

isotopic fractionation

T or F: The MPN technique is rarely applied in the food industry because any microbial presence in food is unsafe.

FALSE

T or F: The diversity of microorganisms in culture collections is representative of the diversity of microorganisms found in nature.

FALSE

The term axenic is used to describe a(n)

pure culture.

When dealing with stable isotopes, enzymes tend to favor

the lighter isotope.

The phylogenetic analysis of complex microbial communities often targets small subunit (SSU) ribosomal RNA genes. This is because rRNA is found in all organisms and __________.

is highly conserved over evolutionary time

What is the process that will amplify DNA from a single cell isolated from a natural microbial community?

multiple displacement amplification

A NASA ecologist wants to design an instrument to send to Mars on the next space probe to determine whether living organisms ever carried out carbon fixation on that planet. Suggest an assay that she could use on Martian soil samples.

13C/12C stable isotope analysis

T or F: Once a putative pure culture has been obtained from the environment, it is no longer necessary to check its purity.

FALSE

Which of the following statements is FALSE concerning enrichment bias?

Enrichment bias favors organisms that grow quickly. (FALSE)

T or F: In natural samples it is often difficult to differentiate live cells from dead cells or cells from nonliving matter.

TRUE

T or F: Several fluorogenic dyes can be used simultaneously in a sample as long as they each emit light at a different measurable wavelength.

TRUE

How do viability stains usually distinguish between living cells and dead cells?

The dye specifically targets intact cytoplasmic membranes.

A study has begun on the microbial community in the lake at different times of the year. In order to quickly determine the approximate number of reproducing bacteria in a sample, it would best to use __________.

a fluorescent viability stain

Winogradsky columns are used primarily for enrichment of

aerobes, anaerobes, and phototrophs.

You would like to determine the rate of production of carbon dioxide in a specific microbial habitat. How could you do this without growing the microorganisms in the lab?

by using a microsensor

The element(s) that have proven useful for stable isotope studies are

carbon, nitrogen, and sulfur.

The methodology of microbial ecology includes

enrichment and isolation of specific microbes, cell-staining, and gene, transcript, and protein characterization.

What technique(s) can be used to characterize the phylogenetic composition of a microbial community without culturing any of the members?

fluorescent in situ hybridization

Which molecular method allows for the detection of a specific organism within a diverse microbial community?

fluorescent in situ hybridization

Metatranscriptomics and metaproteomics are favored over metagenomics when ________ is of more interest than ________.

function or gene expression / gene presence

Microarrays are useful for assessing

gene expression and the presence of specific rRNA sequences.

For microbial biodiversity studies, it is common to identify the ________ rather than the ________ as a measure of biodiversity.

genes / organisms themselves

Culture-independent approaches avoid issues associated with

growing organisms in the lab.

The science of microbial ecology deals with

how the activity and biodiversity of microbial communities affect microbial interactions with each other and the environment.

Microarrays that have been designed to screen samples for specific groups of bacteria are called __________.

phylochips

Genes that change over evolutionary time as organisms diverge are called orthologs. Organisms with identical or very similar orthologous genes belong to the same __________.

phylotype

Phylogenetic stains, such as those used in FISH, hybridize with

ribosomal RNA.

Metagenomics involves the analysis of a microbial community by __________.

sampling and sequencing all of the genes in an environment

Enrichment cultures are often effective for isolating bacteria from complex communities in natural samples because they __________.

select both for and against certain bacteria

Which fluorescent molecule enables visualization of living microorganisms?

GFP

Analyses of sulfur isotopes have been used as evidence against life on the Moon, because the sulfides in lunar rocks have

an isotope composition similar to igneous rocks.

The biggest limitation of traditional light microscopy and electron microscopy methods is that they are unable to reveal

genetic and functional diversity of microorganisms in the habitat under study.

Select the option that lists the steps necessary for PCR microbial community analysis in the correct order.

microbial sample collection; DNA extraction; PCR of target genes; sorting by electrophoresis; analysis

Which technique would be used to estimate the concentration of naturally occurring Escherichia coli in a wastewater sample?

most probable number (MPN) method

The best choice for estimating the viable cell number of a water sample would be the __________.

most probable number method