CH 34

Body odor is largely due to which one of these?

Bacterial degradation of lipids

In humans, the acquisition of a normal microbiota normally begins _____.

at birth

Propionate is formed as a fermentation product of the gut microbiota. Its two roles in metabolism are to _____ and _____.

inhibit cholesterol synthesis in the liver increase synthesis of hunger-suppressing hormones

Bacteria in the gut secrete enzymes to break down _____, which are then fermented into short-chain fatty acids like butyrate, propionate, and acetate.

polysaccharides to monomers

Although the human microbiome is dominated by five major phyla, at the species level, the average adult gut hosts _____ different microbial species.

500-1,000

Which of the following statements regarding the core microbiome is false?

A core microbiome is found in an individual throughout his/her life, regardless of environmental conditions.

Which of the following statements regarding the functional core microbiome is false?

A functional core microbiome has been identified for the human gut, and is a list of common genera.

Match each bacterial species that forms part of the normal microbiota of the mouth with the correct description.

Anaerobes such as Porph --> among the first colonizers after the teeth erupt Streptococcus mutans and --> attach to enamel surfaces of teeth Streptococcus --> in saliva and attached to buccal and gingical epithelia surfaces

Which of these results in increased numbers of beneficial bifidobacteria in a child's intestinal tract?

Breast feeding

Identify the false statement regarding the development of a stable microbiome.

By the end of its first year, a child has developed an adult-like community of human-associated microbes.

Which of the following statements regarding the use of probiotics on livestock is false?

Chickens show reduced carriage of Helicobacter by treatment with a probiotic strain of Bacillus subtiis.

Which bacterial species is most closely associated with the development of the skin condition called acne vulgaris?

Cutibacterium acnes

Identify the false statement regarding the use of probiotics on livestock.

Day-old lambs are treated with a blend of 29 bacteria to help establish a health microbiome.

The early colonization of the infant intestinal tract by _____ and _____ appears to establish a reducing environment for the growth of anaerobes such as bifidobacteria and bacteroidetes.

E. coli streptococci

True or false: The anatomy and physiology of human skin do not vary, therefore the normal microbiota of the skin is consistent throughout the body.

False

In addition to Actinobacteria and Fusobacteria, which three of the following are major phyla found on human skin, in the intestinal tract, and other mucosal surface?

Firmicutes Proteobacteria Bacteroidetes

In the duodenum, the low number of bacteria present are mostly _____.

Gram-positive

To reduce the production of volatile unsaturated fatty acids, many deodorants contain antimicrobial substances that selectively inhibit which of these?

Gram-positive bacteria

Identify the false statement regarding the human microbiome.

Identical twins must have identical microbiomes.

In which body region do bacteria contribute to these conditions: caries, gingivitis, and periodontitis?

Mouth

Which of the following statements regarding experiments with germ-free (GF) mice and serotonin is false?

Serotonin is primarily produced in the brain, but also acts in the GI tract.

Which of the following statements regarding the human microbiome is false?

The healthiest human microbiome is found among vegetarians who don't use tobacco.

Which of the following statements reflects current thinking about the microbiota of the respiratory tract?

The lower respiratory tract is not sterile.

Which of the following statements concerning the microbiota of the respiratory tract is false?

The lower respiratory tract is sterile.

Which of the following statements regarding the development of a stable microbiome is false?

The normal community of human-associated microbes begins developing before a child is born.

Which of the following statements regarding toxic peptides is false?

Toxic peptides are produced exclusively by Gram-negative Enterobacteriaceae.

The human microbiome is best described as _____.

all the microbes that reside in and on a human body

Certain human viruses cause their host cells to become cancerous by which two mechanisms?

altering the host cell cycle preventing DNA damage repair

Bacteriocins kill target bacteria by forming pores and depolarizing membranes. Chemically, bacteriocins are _____.

amphipathic peptides

Which of the following pairs of sites on the body can be expected to have highly similar microbiomes?

an individual's left forearm, sampled twice, a week apart

In addition to bacteria, which three of the following are also present in the human microbiome?

archaea viruses fungi

Animals that eat a meat-intensive diet introduce L-carnitine and phosphatidylcholine to their GI tract, where microbial metabolism converts them to trimethylamine. This compound is later oxidized in the liver to trimethylamine N-oxide, which is associated with the development of ______.

atherosclerosis

Toxic peptides produced by Gram-positive bacteria that target closely related strains or species are termed _____.

bacteriocins

Viruses that alter their host cell cycle to promote proliferation and that prevent host cells from repairing DNA damage are responsible for the host cell _____.

becoming cancerous

The early colonization of the infant intestinal tract by E. coli and streptococci appears to establish a reducing environment for the growth of which anaerobes?

bifidobacteria bacteroidetes

Secretory IgA (SIgA) molecules coat mucosal surfaces where they _____.

bind their microbial targets to promote clearance of foreign antigens

Germ-free mice have limited development of the white blood cells of the innate immune system, all cells that mature in the _____.

bone marrow

Host intestinal cells are induced to produce serotonin in response to gut bacteria that produce _____.

butyrate

The skin bacterium Propionibacterium acnes breaks down lipid secretions to unsaturated fatty acids, some of which have strong antimicrobial activity against which two types of microbes?

certain fungi Gram-negative bacteria

Bacteriocins are toxic peptides produced by Gram-positive bacteria that target _____.

closely related strains or species

The idea that a healthy gut microbiome is protective against the establishment of pathogens in the gut is termed _____.

colonization resistance

The core microbiome is a group of microorganisms that is _____.

consistent among people who share a common feature

In addition to short chain fatty acids produced by the gut microbiota, immune cell maturation also requires _____ released by intestinal immune cells.

cytokines

Match each area of the human small intestine with the best description of the normal microbiota found there.

duodenum --> low numbers, mainly gram-positive cocci and rods Ileum --> anaerobic gram-neg Enterobacteriaceae Jejunum --> Candida albicans, Enterococcus facealis

The contribution of the microbiome to disease is called

dysbiosis

The contribution of the microbiome to disease is called _____

dysbiosis

The gut microbiota releases the fermentation product butyrate which helps to keep the oxygen tension low, thereby _____.

favoring the growth of anaerobes

Bacteriocins are amphipathic peptides that kill target bacteria by _____ and _____. [Choose two.]

forming pores depolarizing plasma membranes

Microbes that provide the host with a suite of activities required for health and homeostasis are termed the _____.

functional core microbiome

Which three of these are correct descriptions of human skin?

high salt concentration dry in many areas some areas have sebum

B cells that differentiate into secretory IgA-producing plasma cells are located _____.

in the gut-associated lymphoid tissue

Both mice and humans exhibit which two of the following changes in the gut microbiota in obesity?

increased Firmicutes decreased Bacteriodetes

Metabolic endotoxemia refers to a change in the diet that leads to dysbiosis and the presence of _____ to the blood.

lipopolysaccharide

A dietary change that leads to dysbiosis and the presence of lipopolysaccharide to the blood results in a series of events termed _____.

metabolic endotoxemia

The biochemicals secreted by bacteria in the gut that act on host cells are collectively termed the _____.

metabolome

The term used to describe all the microbes that reside in and on a healthy host is _____.

microbiome

Toxic peptides produced by some bacteria that kill closely related strains are termed _____ if they are made by a wide range of Enterobacteriaceae and _____ if they are produced by E. coli.

microcins; colicins

The idea that we can host so many microbes and foreign food antigens in our gut without responding with an overwhelming inflammatory response is termed _____.

mucosal tolerance

In a healthy human, which of the following tissues is normally colonized by microorganisms?

mucous membranes

In a healthy human, which of the following tissues is normally free of microorganisms?

muscles

Microbes commonly associated with the human body are known as microbiota.

normal

Microbes commonly associated with the human body are known as _____.

normal microbiota

An increased concentration of Firmicutes and a decreased concentration of Bacteroidetes in the gut is often correlated with _____.

obesity

Compounds added to foods or supplements to enhance the colonization and health benefits of other microorganisms are termed .

prebiotics

Live microorganisms, which when administered in adequate amounts confer a health benefit to the host, are termed .

probiotic

Live microorganisms, which when administered in adequate amounts confer a health benefit to the host, are termed _____.

probiotics

Breastfeeding is important in the development of an infant's intestinal microbiota because human milk _____.

promotes growth of bifidobacteria

Following fermentation of carbohydrate monomers, the short-chain fatty acid _____ travels to the liver where it inhibits cholesterol synthesis.

propionate

Classifying certain probiotics as drugs has the consequence of _____.

requiring safety and efficacy clinical trials

Immune cell maturation requires _____ produced by the gut microbiota as well as cytokines released by intestinal immune cells.

short chain fatty acids

Bacteria in the gut secrete enzymes to break down complex polysaccharides into their constituent monomers. These monomers are then fermented into _____.

short-chain fatty acids

Germ-free mice exhibit anatomic differences in tissues other than in the gut, specifically in the _____, where these tissues were underdeveloped. [Choose three.]

spleen thymus lymph nodes

Microcins and colicins can inhibit which three of the following?

tRNA synthetase cell wall synthesis transcription

Two challenges to the use of probiotics to treat humans are that _____ and _____.

the health benefits have not been rigorously tested it is difficult to evaluate whether probiotics colonize the gut

In the gut, the growth of anaerobes is favored over facultative anaerobes by _____.

the low oxygen tension

The metabolome is best described as _____.

the metabolic products secreted by bacteria

Colonization resistance refers to the idea that _____.

the microbiota in the gut is protected from disease by the presence of a healthy community

Babies born vaginally acquire most of their initial microbiota from _____.

their mother

Animals that eat a meat-intensive diet introduce L-carnitine and phosphatidylcholine to their GI tract, where microbial metabolism converts them to _____.

trimethylamine

Some Gram-negative bacteria deliver bacteriocidal toxins directly through the cell envelope of competing bacteria through their _____.

type VI secretion system

Germ-free mice exhibit anatomic differences in tissues other than in the gut, specifically in the spleen, thymus, and lymph nodes, where these tissues were _____.

underdeveloped

Mucosal tolerance explains how _____.

we can host many microbes and foreign food antigens in our gut without responding with an overwhelming inflammatory response

Germ-free mice have limited development of the _____ cells of the innate immune system.

white blood