Microbiology Midterm 1

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What role do appendages and holdfasts play in the survival of aquatic bacteria?

They allow bacteria to attach to surfaces in water, helping them access nutrients and resist flushing by currents.

Describe the primary function of phytoplankton in the ocean environment.

Phytoplankton, such as cyanobacteria, primarily fix carbon and nitrogen through photosynthesis, supporting marine food webs.

Explain how the anaerobic conditions in the profundal zone affect microbial life.

The low oxygen levels in the profundal zone stimulate the growth of anaerobic bacteria, which carry out processes like sulfate reduction.

What is the significance of bioluminescence in luminescent bacteria?

Bioluminescence aids luminescent bacteria in symbiotic relationships by attracting prey for benthic-dwelling fish. Signup and view all the answers

Why are purple and green sulfur bacteria typically found deeper in freshwater rather than at the surface?

They require low light conditions to thrive, which are more prevalent in deeper waters where photosynthesis is less active. Signup and view all the answers

What are healthcare-associated infections and why are they significant?

Healthcare-associated infections are infections acquired while receiving treatment in a healthcare facility, known as nosocomial infections, and they affect 1 in 25 hospital patients. Signup and view all the answers

Define a compromised host and provide an example.

A compromised host is an individual whose resistance to infection is weakened due to factors like disease or therapy, such as a cancer patient undergoing chemotherapy. Signup and view all the answers

List three risk factors contributing to healthcare-associated infections.

The three risk factors are microorganisms in the hospital environment, the weakened status of the host, and the chain of transmission within the hospital. Signup and view all the answers

Explain how healthcare-associated infections can be prevented.

HAIs can be prevented through rigorous hygiene practices, proper sterilization of medical instruments, and effective protocols to control disease transmission. Signup and view all the answers

Why is it often insufficient for a single risk factor to cause healthcare-associated infections?

It is often insufficient because HAIs typically result from a combination of the three risk factors, whereby one alone may not trigger an infection. Signup and view all the answers

What is the common name for microbes that convert soil nitrogen into a mobile form for plant nutrition?

Nitrogen-fixing bacteria Signup and view all the answers

What process do bacteria of the genus Pseudomonas use fully oxidized nitrogen as an electron acceptor?

Denitrification Signup and view all the answers

Which group of bacteria oxidizes H2S to produce NADH in the sulfur cycle?

Chemoautotrophic bacteria Signup and view all the answers

In the sulfur cycle, what form of sulfur do plants assimilate for amino acid and protein synthesis?

Sulfates Signup and view all the answers

What type of respiration do some microbes like Desulfovibrio perform using oxidized forms of sulfur?

Anaerobic respiration Signup and view all the answers

What is the primary form of phosphorus that exists in ecosystems?

Phosphate ions Signup and view all the answers

How does Acidithiobacillus contribute to the phosphorus cycle?

By producing acid that solubilizes phosphate in rocks Signup and view all the answers

Why does phosphorus tend to accumulate in the sea rather than returning to the atmosphere?

There are no volatile phosphorus-containing products. Signup and view all the answers

What process is used to sterilize paper and plastic in aseptic packaging?

Hot hydrogen peroxide or UV light. Signup and view all the answers

What type of radiation is primarily utilized for food preservation and how is it measured?

Ionizing radiation, measured in Grays. Signup and view all the answers

What metabolic group of anaerobic bacteria is especially encouraged by the operation of a sludge digestion system?

Methanogens are the metabolic group of anaerobic bacteria encouraged by sludge digestion systems. Signup and view all the answers

At what dose range is ionizing radiation effective at sterilizing higher animals?

0.005–0.1 kGy. Signup and view all the answers

What is the relationship between biochemical oxygen demand (BOD) and the welfare of fish?

Higher BOD levels can deplete oxygen in water, negatively affecting fish welfare. Signup and view all the answers

Which organisms require the highest radiation doses for sterilization and what are their dose levels?

Bacterial endospores, needing 10–50 kGy. Signup and view all the answers

What are the key differences between thermophilic anaerobic spoilage and flat sour spoilage by mesophilic bacteria?

Thermophilic anaerobic spoilage occurs at high temperatures, while flat sour spoilage involves mesophilic bacteria at moderate temperatures. Signup and view all the answers

Explain how microwaves sterilize food even though they do not cause ionization.

Microwaves cause water molecules to oscillate, generating heat through friction. Signup and view all the answers

Name two methods of food preservation that utilize high pressure.

High Pressure Processing (HPP) and Pressure-Assisted Thermal Sterilization (PATS) are two methods utilizing high pressure. Signup and view all the answers

What is the purpose of Hazard Analysis and Critical Control Point (HACCP) in food safety?

HACCP identifies critical points in food production where contamination may occur. Signup and view all the answers

What must be done to foods prior to being filled into aseptic packages?

Foods must be sterilized before filling. Signup and view all the answers

What is the impact of ionizing radiation on viruses according to the information provided?

Viruses require doses of 10–200 kGy to be effectively sterilized. Signup and view all the answers

What happens to packages in aseptic packaging once they are sealed?

The packages are not sterilized after sealing. Signup and view all the answers

Why is it necessary to specify 'fecal' coliform in water pollution testing?

It specifies that the coliform bacteria are sourced from fecal matter, indicating potential health risks from contaminated water. Signup and view all the answers

How do flocculants like alum aid in water treatment?

Flocculants such as alum coagulate colloidal impurities and microorganisms, allowing them to settle out during sedimentation. Signup and view all the answers

What is the primary role of the activated sludge system in secondary sewage treatment?

It aerates wastewater, promoting the growth of aerobic microbes that metabolize organic matter and significantly reduce BOD. Signup and view all the answers

What is the expected percentage of BOD removal in secondary sewage treatment using trickling filters?

Trickling filters typically remove 80–85% of BOD from sewage. Signup and view all the answers

In sewage treatment, what does sludge digestion accomplish?

It breaks down organic solids in sedimented sludge using anaerobic bacteria, producing methane and carbon dioxide. Signup and view all the answers

What is the function of oxidation ponds in sewage treatment?

Oxidation ponds allow for settling of sludge and support aerobic decomposition, cultivating algae for oxygen production. Signup and view all the answers

What constitutes tertiary sewage treatment?

Tertiary sewage treatment involves the removal of remaining BOD, nitrogen, and phosphorus through physical and chemical treatments. Signup and view all the answers

Why is chlorination used before releasing treated sewage?

Chlorination disinfects the sewage, killing harmful microorganisms to ensure safe water release. Signup and view all the answers

What is the primary purpose of primary sewage treatment?

Its main purpose is to remove solids and reduce BOD by approximately 25–35%. Signup and view all the answers

What distinguishes fecal coliforms from total coliforms in water quality testing?

Fecal coliforms specifically indicate contamination from human or animal waste, whereas total coliforms may originate from various environmental sources. Signup and view all the answers

Aquatic Microbiology

The study of microorganisms and their activities in natural water bodies.

Littoral Zone

The zone along the shore with rooted vegetation.

Limnetic Zone

The surface of open water away from the shore where photosynthetic algae thrive.

Profundal Zone

The deeper water beneath the limnetic zone with low oxygen levels, where anaerobic bacteria flourish.