Environmental Microbiology Question Bank Flashcards

Flashcards covering key concepts, analytical techniques, calculations, and environmental microbiology principles from the lecture question bank.

Which list contains the three domains of cellular life?

Bacteria, Archaea, and Eukarya

Which microbial group produces methane in the anoxic habitat of the rumen?

Archaea

What is the primary function of bacterial ribosomes?

Protein synthesis

Why do viruses require susceptible living cells for replication?

They depend on host cellular machinery

What does microbial population growth primarily mean?

An increase in cell number

What can a Gram stain provide as an initial identification step?

A preliminary cell-envelope classification

Which interaction provides a measurable benefit to both partners?

Mutualism

What is the rhizosphere?

Soil influenced by plant roots

What does a plant supply to its mycorrhizal fungal partner?

Photosynthetically fixed carbon

Which rumen microbial products provide an important energy source to the ruminant?

Volatile fatty acids

What best describes a biofilm?

An attached microbial community embedded in a matrix

What does biochemical oxygen demand (BOD) estimate?

Oxygen used to oxidize biodegradable organic matter

Which material can be part of a bioaerosol?

Airborne microorganisms and biological fragments

Endotoxin is associated with which bacterial structure?

 The outer membrane of Gram-negative bacteria

Which bacterium causes Q fever?

Coxiella burnetii

What is a pathogen reservoir?

A population or environment that maintains a pathogen over time

What does AMR stand for?

Antimicrobial resistance.

Pasteur’s sterile swan-neck broth remained clear while air entered. What did this support?

Growth required contamination by material carrying microorganisms

A student obtains a well-isolated colony from a mixed manure sample. What should happen before calling it a pure culture?

Subculture it and verify purity

A medium suppresses competing bacteria and changes color after a metabolic reaction. How is it classified?

Selective and differential

Two DNA extracts are tested with the same validated qPCR assay and comparable efficiency. Which interpretation is appropriate for a lower quantification cycle?

More starting target DNA is usually present

A sample gives no target amplification, and its internal amplification control also fails, while external positive controls work. What should be investigated first?

Sample inhibition or reaction failure

Which measure describes microbial diversity within a single sample?

Alpha diversity

Why can hydrogen consumption by methanogens help a partner’s anaerobic metabolism?

It removes a product and keeps the partner’s reaction energetically favorable

Why is oxygen control important in a legume nodule?

Nitrogenase needs protection from oxygen while energy must still be supplied

Which process converts ammonium through nitrite to nitrate under aerobic conditions?

Nitrification

Which conditions favor biological nitrate removal by denitrification in a treatment plant?

Anoxic conditions with an available electron donor

Native contaminant degraders are present, but a nutrient shortage limits their activity. Which strategy directly addresses this limitation?

Biostimulation

Why is some settled activated sludge returned to the biological reactor?

To maintain the reactor’s microbial population

 An air sample is PCR-positive but culture-negative. Which conclusion is justified by these results alone?

Target DNA was detected, but viability and infectivity remain unresolved

Stream water contains 200 gene copies per liter and flows at 5 liters per second. What is the estimated instantaneous geneload?

1,000 copies per second

Illness follows ingestion of a toxin that bacteria produced in food before consumption. What is this mechanism?

Food intoxication

A bacterium acquires free DNA from its surroundings. Which transfer mechanism is involved?

Transformation

Why should visible manure be removed before farm disinfection?

It can shield organisms and reduce active disinfectant availability

A plate inoculated with 0.1 mL of a 10⁻⁴ dilution yields 80 colonies. What is the estimated original concentration, assuming a countable representative plate?

8 × 10⁶ CFU/mL

Taxon X rises from 10% to 20% of reads after treatment. Total bacterial abundance falls from 10⁸ to 10⁷ cells/mL. Assuming read fractions represent cell fractions, what happens to X?

It falls from 10⁷ to 2 × 10⁶ cells/mL

Low-biomass water samples and extraction blanks contain similar target signals. What is the best next step before a biological interpretation?

Investigate reagent contamination and repeat with appropriate controls

Two isolates have nearly identical 16S rRNA gene sequences but different disease associations. What is the most appropriate conclusion?

16S similarity alone may lack the resolution to distinguish them

A suspected pathogen cannot be grown in pure culture and occurs in healthy carriers. How should disease causation be assessed?

Use converging clinical, epidemiological and molecular evidence with suitable controls

A bacterial inoculant inhibits a plant pathogen on agar. Which field study best tests its practical benefit?

A replicated inoculated-versus-control trial measuring establishment and plant disease

A contaminant declines only while microbes receive a different growth substrate; decline stops when that substrate is removed. What best explains this pattern?

Co-metabolism dependent on the growth substrate

Pathogen counts fall in water after settling, while sludge counts rise. What is the best interpretation?

Separation transferred part of the pathogen burden to sludge

A bioremediation trial shows a fall in the parent contaminant. What additional evidence is most important before claiming successful detoxification?

Transformation products and their toxicity

Treatment reduces BOD from 100 to 40 mg/L, but flow rises from 1,000 to 3,000 L/day. What happens to daily BOD load?

It rises from 100 to 120 g/day

A poultry worker moves between tasks and ventilation zones. Which design best estimates the worker’s airborne exposure?

Personal breathing-zone sampling linked to task and time records

An antibiotic residue is below the susceptible strain’s MIC, but resistant cells increase relative to susceptible cells during exposure. What does this show?

Selection can occur below MIC without requiring visible-growth inhibition

An ARG falls from 10⁶ to 5 × 10⁵ copies/g dry manure, while a bacterial reference falls from 10⁸ to 10⁷ copies/g. Which interpretation is correct?

ARG copies/g fall, while the ARG-to-reference ratio rises fivefold

A compost core reaches the target temperature, but cooler edges are not turned inward. What is the most defensible assessment?

Whole-pile treatment has not been demonstrated

New animals test negative on arrival at a farm. What is the best basis for release from isolation?

Pathogen-specific timing, testing and release criteria

Human cases and a food isolate have matching sequences. Which additional findings most strengthen attribution to a food lot?

Shared consumption histories and supplier records converging on that lot