Micro 302 Iowa State University Exam 5/Final HW and quizzes

The role of the iron-containing leghemoglobin in the rhizobial root nodules of soybeans is to __________.

lower the amount of free O2 in the root nodule

Most nitrogen-fixing bacteria symbiotically associated with plants are called

rhizobia

In mycorrhizal mutualisms between plants roots and fungi

the plant supplies carbohydrates to the fungus and the fungus supplies phosphorus and nitrogen to the plant.

When squids that contain luminescent bacterial symbionts hatch, they do NOT contain a bacterial symbiont. Symbiont transmission in this symbiosis is

horizontal and involves specific selection of the symbiont from the environment.

Bacterial symbionts most often provide marine invertebrates in hydrothermal vents with

fixed carbon dioxide in the form of organic compounds.

T/F: Due to the close interactions with their hosts, obligate symbionts generally have larger genome sizes compared to other non-symbiotic bacteria.

false

The human microbiome contains all

organisms present in and on the body.

T/F: Normal microbiota is usually found in the blood, lymph, and nervous systems of the body.

false

Helicobacter pylori is a bacterium found in the stomachs of roughly half of the human population. It is considered to be a pathogen because __________.

it can cause chronic inflammation

The colon has been described as a living fermentation vessel. Which type of culture system would it most resemble?

continuous culture

The most heavily colonized human organ by bacteria is the ________, containing 10111012 bacterial cells per gram.

large intestine

Obligate anaerobes are likely to be found in the __________.

colon

The human oral microbiota consists of

diverse aerobic and anaerobic microorganisms.

Which of the following is the genus represented by the greatest diversity of phylotypes on the skin?

Actinobacteria

Gut microbiota is known to be linked with

obesity and inflammatory bowel syndrome.

Weight gain and obesity may be partly caused by certain gut microbial communities that

produce more volatile fatty acids by fermentation.

Which of the following is NOT important for the adherence of bacteria to host tissues?

lipopolysaccharides

The best term to describe the general process by which microorganisms cause diseases is known as

pathogenesis.

The process by which white blood cells ingest and kill bacteria is called

phagocytosis.

The spread of pathogens through the blood and lymph systems that results in a bloodborne systemic infection is called

septicemia.

A pathogen must __________ in order for it to cause disease.

attach and multiply

A researcher wanted to determine the LD50 (lethal dose that kills 50% of the infected hosts) for a newly isolated bacterial pathogen. Mice were inoculated with diluted cultures containing between 101 and 107 cells. After two days, all of the mice had died EXCEPT for the uninoculated controls. Which of the following is the most likely explanation?

This pathogen is highly virulent in mice.

Capsules are particularly important for

protecting bacteria from host defense mechanisms.

It is thought that attenuation occurs especially in a laboratory setting because

nonvirulent or weakly virulent mutants grow faster in laboratory media when there is no selective advantage to virulence.

Which of the following is most likely to cause disease?

injection of 105 cells of a highly virulent bacterial species into a mouse

T/F: An opportunistic pathogen causes disease ONLY in the presence of normal host resistance.

false

T/F: Pathogenicity islands are clusters of genes for virulence factors that are located together on the bacterial chromosome.

true

Siderophores are

organic molecules that help pathogens take up iron.

All AB toxins have which of the following?

two subunits

Tetanus toxin causes

muscles to be unable to relax.

T/F: Clostridium botulinum are endospore-forming bacteria normally found in the soil.

true

Staphylococcus aureus and Streptococcus pyogenes strains can produce ________ that cause the severe and sometimes life-threatening symptoms of toxic shock syndrome.

superantigen toxins

The exotoxin that functions by destroying cell membranes is called __________.

a cytolytic toxin

Exotoxins are ________, but endotoxins are ________.

proteins / lipopolysaccharide-lipoprotein complexes

Compared with an endotoxin, would a bacterial exotoxin generally be more likely to function after it had been significantly heated?

No, because exotoxins are heat-labile and less resistant to heating than endotoxins.

The phyllosphere of a plant is found ___.

on the leaves

You are designing a bioremediation scheme where you add bacteria that consume oil to an oil spill to degrade the pollutant. This is an example of ___.

bioaugmentation

Which bacteria listed below is best known for its ability to colonize legume roots and fix nitrogen?

Rhizobia

The microbe that is most closely associated with dental caries is ___.

Streptococcus mutans

Which of the following bacterial phylotypes is associated with the large intestine gut microbiome in a healthy individual?

Firmicutes

T/F: Secondary infections are often bacteria that infect after viral infection.

true

What disease is caused by Streptococcus pneumoniae?

pneumonia

Superantigens and endotoxin are ___.

dangerous due to overstimulation of the immune response

Pathogenicity islands are ___.

genes found in the DNA of a pathogen

Superantigens cause disease by ___.

overactivating T cells

Which of the following is another term for antibodies?

immunoglobins

Cells that can engulf foreign particles, and can ingest, kill, and digest most bacterial pathogens are called

phagocytes

The rapid increase in adaptive immunity after a second antigen exposure is called

immune memory

MHC I proteins are found

on all nucleated cells

Which of the following are proteins that interact directly with antigens during the adaptive immune response?

-major histocompatibility complex
-T cell receptors (receptors on T cells)
-immunoglobins

An example of pathogen-associated molecular patterns (PAMP) is

lipopolysaccharide (LPS).

Neutrophils are the most abundant phagocytic cells. How do they differ from other phagocytic cells?

They are common in pus and at the site of acute inflammation

The unique antigen-reactive proteins of T cells are

T cell receptors.

DiGeorges syndrome is a developmental defect that prevents the maturation of the thymus. What cell type would be reduced by this condition?

T cells

Pattern recognition receptors (PRRs) are found on which of the following cells?

macrophages and neutrophils

Which of the following interact with toll-like receptors (TLRs)?

bacterial LPS

The increased rate of O2 uptake by activated phagocytes is called the

respiratory burst.

How can sepsis lead to hypotensive shock?

Vasodilation and increased vascular permeability occur on a large scale, resulting in a drop in blood volume and therefore a drop in blood pressure.

Enhanced phagocytosis of antibody-sensitized cells is known as

opsonization.

Interferons function to fight which type of pathogen?

viral

One of your first ideas is to look at probiotics to enhance the host's normal microbiota. The use of probiotics to stimulate the normal intestinal microbiota and promote general health has gained increasing popularity in recent years. There are several ways in which our normal microbiota protects us from infection. Which of the mechanisms below is not a protective mechanism of our normal microbiota?

Normal microbiota spreading to locations where they are not normally found to prevent colonization from pathogens.

Phagocytosis eliminates pathogens that have evaded the first line of defense. The process can be broken down into six main steps. Enhancing any of those steps could lead to more efficient bacterial elimination during infection.

Chemotaxis
Adherence
Ingestion
Maturation
Killing
Elimination

The complement cascade involves a series of proteins that circulate in the blood. There are three pathways that lead to activation of the complement cascade--classical, alternative, and lectin. Your goal is to enhance the immediate response to bacterial infection. With this goal in mind, why might you choose to target the lectin or alternative pathways rather than the classical?

Neither pathway relies on antibodies.

Targeting inflammation as an infection control mechanism is a double-edged sword. On one side, inflammation evolved to help eliminate and/or contain pathogens. On the other, too great of an inflammatory response will lead to tissue destruction and lasting damage. You decide to focus on the process of margination during inflammation. Predict the most likely outcome of enhancing margination.

enhanced phagocytosis

Antibody-mediated immunity is particularly effective against

extracellular pathogens.

T/F: Tolerance is the acquired ability to make an adaptive immune response directed to self-antigens.

false

Somatic hypermutation occurs only in the ________ regions of rearranged heavy and light chains.

V

Paracrine actions of cytokines will cause effects on ____.

a nearby cell

The heat that is associated with inflammation is ____ and is one of the 4 cardinal signs of an inflammatory response.

calor

Lysozyme is found in human tears and will ___.

break down peptidoglycan

TLR4 is mutated and nonfunctional in C3H/HeJ mice. Because of this, these mice are ___.

less sensitive to LPS

Which antibody is a pentamer and the first to appear upon antigen exposure?

IgM

MHC Class I molecules are found ___ and present antigen to ____ T cells.

on all nucleated cells: cytotoxic

Affinity maturation relies on ____ and differential binding strength during clonal selection.

somatic mutations

If a macrophage engulfs and kills a bacterial cell, it will present parts of this cell (antigens) on its ___ for ___.

MHC II: Helper T cells

What did the Mackaness experiment demonstrate?

?

A pre-T cell that reacts too strongly to self antigen will ___.

fail negative selection and be killed

Systemic inflammation is generally ___.

harmful to the host

PAMPS are found on ___.

foreign cells

Which antibody is the most prevalent circulating antibody and makes up most of a secondary immune response?

IgG

Granzymes and perforin are found in ___.

cytotoxic T cells

You get a booster shot for your MMR vaccine so that your ___ response will be adequate if you're exposed to measles or mumps.

secondary response

Resident leukocytes can release _____ which provides communication between white blood cells.

cytokines

The most numerous leukocytes in a healthy individual are _____.

neutrophils

Antigens like viral particles and toxins in solution are recognized by ___.

B cells and antibodies