Chapter 34: The Microbe-Human Ecosystem
Although the human microbiome is dominated by five major phyla, at the species level, the average adult gut hosts _____ different microbial species. millions of 500-1,000 tens of thousands of a few dozen
500-1,000
Which of the following statements regarding the core microbiome is false? The core microbiome is usually described at the level of genus. The core microbiome collectively accomplishes specific metabolic functions. A core microbiome is found in an individual throughout his/her life, regardless of environmental conditions. A core microbiome describes a group of taxa consistent among a population with a common feature.
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. A functional core microbiome includes those microbes that contribute to the development of the immune system. The synthesis of vitamin K by Escherichia coli is one part of the functional core microbiome. The community metabolism in the microbiome is a more important measure than the individuals responsible for that metabolism.
A functional core microbiome has been identified for the human gut, and is a list of common genera.
Body odor is largely due to which one of these? Bacterial degradation of lipids Dead and dying bacteria on the skin Bacterial fermentation of sugars Accumulation of sweat
Bacterial degradation of lipids
Which of these results in increased numbers of beneficial bifidobacteria in a child's intestinal tract? Bottle feeding instead of breast feeding Adding solid food to the diet Switching from breast milk to cow's milk Breast feeding
Breast feeding
Identify the false statement regarding the development of a stable microbiome. An adolescent has a different community of microbes than her grandmother, despite sharing a home. Early childhood is a critical time for establishing a healthy microbiome to help the immune system mature. The normal community of human-associated microbes begins at the moment of birth. By the end of its first year, a child has developed an adult-like community of human-associated microbes.
By the end of its first year, a child has developed an adult-like community of human-associated microbes. (not until the third year)
Which of the following statements regarding the use of probiotics on livestock is false? Beef cattle show reduced carriage of E. coli O157:H7 when treated with Lactobacillus acidophilus. Chickens show reduced carriage of Helicobacter by treatment with a probiotic strain of Bacillus subtiis. Use of probiotics may decrease antibiotic use in large scale livestock processing.
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? Staphylococcus epidermidis Staphylococcus aureus Cutibacterium acnes Corynebacterium acnes
Cutibacterium acnes
Identify the false statement regarding the use of probiotics on livestock. Use of probiotics may decrease antibiotic use in large scale livestock processing. Chickens show reduced carriage of Campylobacter by treatment with a probiotic strain of Bacillus subtilis. Beef cattle show reduced carriage of E. coli O157:H7 when treated with Lactobacillus acidophilus. Day-old lambs are treated with a blend of 29 bacteria to help establish a health microbiome.
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. Lactobacillus staphylococci E. coli Clostridium streptococci
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. True False
False
In the duodenum, the low number of bacteria present are mostly _____. Gram-positive Gram-negative
Gram-positive
To reduce the production of volatile unsaturated fatty acids, many deodorants contain antimicrobial substances that selectively inhibit which of these? Gram-negative bacteria Gram-positive bacteria Fungi Protists
Gram-positive bacteria
Identify the false statement regarding the human microbiome. There is no single healthy microbiome, but many possible healthy microbiomes. Identical twins must have identical microbiomes. Both breast-fed and bottle-fed infants will develop healthy microbiomes. A history of taking prescription drugs may alter a person's microbiome.
Identical twins must have identical microbiomes.
In which body region do bacteria contribute to these conditions: caries, gingivitis, and periodontitis? Multiple choice question. Respiratory tract Skin Urogenital tract Mouth
Mouth
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? Proteobacteria Firmicutes Spirochaetes Crenarchaeota Bacteroidetes Cyanobacteria
Proteobacteria Firmicutes Bacteroidetes
Which of the following statements regarding experiments with germ-free (GF) mice and serotonin is false? Gut bacteria that produce butyrate induce host cells to produce serotonin. Serotonin is primarily produced in the brain, but also acts in the GI tract. GF mice have much lower blood levels of serotonin compared to conventional mice. Serotonin is involved in mood, appetite, sleep, learning, and memory.
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? Babies born by Caesarean section will develop a healthy microbiome. Each individual's microbiome assembles over time and reflects their experiences. Exposure to medications affects the development of the microbiome. The healthiest human microbiome is found among vegetarians who don't use tobacco.
The healthiest human microbiome is found among vegetarians who don't use tobacco.
Which of the following statements concerning the microbiota of the respiratory tract is false? Multiple choice question. The lower respiratory tract has primarily transient microbes. The upper respiratory tract is colonized by a diverse group of microbes. The lower respiratory tract is sterile.
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 changes throughout an individual's lifetime. By age three years, a child has developed an adult-like community of human-associated microbes. The development of the immune system depends on the community of human-associated microbes. The normal community of human-associated microbes begins developing before a child is born.
The normal community of human-associated microbes begins developing before a child is born.
The human microbiome is best described as _____. all the microbes that reside in the human digestive tract microbes that actively metabolize in and on the human body microbes that are essential to human viability all the microbes that reside in and on a human body
all the microbes that reside in and on a human body
Bacteriocins kill target bacteria by forming pores and depolarizing membranes. Chemically, bacteriocins are _____. phospholipids acidic proteoglycans secondary bile acids amphipathic peptides
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, and his long-term partner's left forearm an individual's left forearm, sampled twice, a week apart an individual's left and right forearms an individual's left forearm and her scalp
an individual's left forearm, sampled twice, a week apart
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 an individual's left forearm, and his long-term partner's left forearm an individual's left forearm and her scalp an individual's left and right forearms
an individual's left forearm, sampled twice, a week apart
In humans, the acquisition of a normal microbiota normally begins _____. during fetal development at about two months of age at birth
at birth
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 ______. diabetes mellitus atherosclerosis double-stranded DNA breaks inflammatory bowel disease
atherosclerosis
Toxic peptides produced by Gram-positive bacteria that target closely related strains or species are termed _____. microcins colicins lectins bacteriocins
bacteriocins
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? Clostridium bacteroidetes Lactobacillus bifidobacteria staphylococci
bacteroidetes bifidobacteria
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? bacteroidetes Lactobacillus staphylococci bifidobacteria Clostridium
bacteroidetes bifidobacteria
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 cytokine production lysis and death protection from superinfection
becoming cancerous
Secretory IgA (SIgA) molecules coat mucosal surfaces where they _____. bind their microbial targets to promote clearance of foreign antigens convert carbohydrates in the diet to short chain fatty acids await stimulation by an antigen compatible with their receptors prevent passage of pathogen cells across the mucosal surface
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 _____. thyroid gut thymus bone marrow
bone marrow
Host intestinal cells are induced to produce serotonin in response to gut bacteria that produce _____. cytokines butyrate microcins polysaccharide A
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? protists certain fungi Gram-positive bacteria Gram-negative bacteria viruses
certain fungi Gram-negative bacteria
Bacteriocins are toxic peptides produced by Gram-positive bacteria that target _____. endospores Gram-negative bacteria most Gram-positive bacteria closely related strains or species
closely related strains or species
The idea that a healthy gut microbiome is protective against the establishment of pathogens in the gut is termed _____. mucosal tolerance probiotic tolerance colonization resistance immune surveillance
colonization resistance
The core microbiome is a group of microorganisms that is _____. found in the large intestine of most individuals variable among individuals over time consistent among people who share a common feature found throughout most individuals
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. toll-like receptors primary bile salts C-type lectins cytokines
cytokines
Which three of these are correct descriptions of human skin? dry in many areas some areas have sebum slightly alkaline high salt concentration warmest part of the body
dry in many areas some areas have sebum high salt concentration
The contribution of the microbiome to disease is called _____ dysbiosis commensalism parasitism inflammation
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 _____. inhibiting the growth of anaerobes lowering the toxicity of small peptides favoring the growth of anaerobes reducing the energy output
favoring the growth of anaerobes
Bacteriocins are amphipathic peptides that kill target bacteria by _____ and _____. [Choose two.] forming pores denaturing the chromosome inhibiting ribosomes depolarizing plasma membranes
forming pores depolarizing plasma membranes
Microbes that provide the host with a suite of activities required for health and homeostasis are termed the _____. gut microbiome functional core microbiome functional core metabolome healthy microbiome
functional core microbiome
Which of the following statements reflects current thinking about the microbiota of the respiratory tract? The lower respiratory tract is not sterile. The lower respiratory tract is colonized by a diverse group of microbes. Both upper and lower respiratory tracts host similar communities of microbes.
he lower respiratory tract is not sterile.
B cells that differentiate into secretory IgA-producing plasma cells are located _____. in the lumen of the gut in the gut-associated lymphoid tissue throughout the bloodstream in the bone marrow
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 elimination of Clostridium increased fungi decreased Bacteriodetes increased Escherichia
increased Firmicutes decreased Bacteriodetes
Propionate is formed as a fermentation product of the gut microbiota. Its two roles in metabolism are to _____ and _____. act as a precursor for lipid synthesis inhibit cholesterol synthesis in the liver stimulate secretion of enzymes to hydrolyze polysaccharide increase colonocyte mitochondrial activity increase synthesis of hunger-suppressing hormones
inhibit cholesterol synthesis in the liver increase synthesis of hunger-suppressing hormones
Two challenges to the use of probiotics to treat humans are that _____ and _____. they cannot be consumed by people with lactose intolerance most probiotic organisms cannot be cultured in the lab it is difficult to evaluate whether probiotics colonize the gut the health benefits have not been rigorously tested
it is difficult to evaluate whether probiotics colonize the gut the health benefits have not been rigorously tested
Metabolic endotoxemia refers to a change in the diet that leads to dysbiosis and the presence of _____ to the blood. pro-inflammatory cytokines short chain fatty acids bacteriocins lipopolysaccharide
lipopolysaccharide
Germ-free mice exhibit anatomic differences in tissues other than in the gut, specifically in the _____, where these tissues were underdeveloped. [Choose three.] urinary tract lymph nodes thyroid spleen thymus meninges
lymph nodes spleen thymus
A dietary change that leads to dysbiosis and the presence of lipopolysaccharide to the blood results in a series of events termed _____. Multiple choice question. musocal immunity metabolic endotoxemia insulin resistance atherosclerosis
metabolic endotoxemia
The biochemicals secreted by bacteria in the gut that act on host cells are collectively termed the _____. metabolome transcriptome metagenome microbiome
metabolome
The biochemicals secreted by bacteria in the gut that act on host cells are collectively termed the _____. transcriptome metagenome metabolome microbiome
metabolome
The term used to describe all the microbes that reside in and on a healthy host is _____. microbiome microgenome microassociation community
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. bacteriocins; colicins colicins; microcins bacteriocins; microcins microcins; colicins
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 _____. immune surveillance mucosal tolerance probiotic tolerance colonization resistance
mucosal tolerance
In a healthy human, which of the following tissues is normally colonized by microorganisms? muscles cerebrospinal fluid mucous membranes blood
mucous membranes
In a healthy human, which of the following tissues is normally free of microorganisms? mucous membranes skin muscles gut
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 metagenomes contaminants opportunistic microbes
normal microbiota
An increased concentration of Firmicutes and a decreased concentration of Bacteroidetes in the gut is often correlated with _____. a vegan diet weight loss obesity viral infection
obesity
Bacteria in the gut secrete enzymes to break down _____, which are then fermented into short-chain fatty acids like butyrate, propionate, and acetate. complex proteins to amino acids long-chain hydrocarbons to acetyl CoA milk proteins to simple sugars polysaccharides to monomers
polysaccharides to monomers
Compounds added to foods or supplements to enhance the colonization and health benefits of other microorganisms are termed __________.
prebiotic
Certain human viruses cause their host cells to become cancerous by which two mechanisms? preventing DNA damage repair altering the host cell cycle altering nuclear import signals generalized transduction generating reactive oxygen species in the viroplasm
preventing DNA damage repair altering the host cell cycle
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 _____. synbiotics prebiotics probiotics
probiotics
Breastfeeding is important in the development of an infant's intestinal microbiota because human milk _____. promotes growth of bifidobacteria inhibits growth of viral pathogens promotes growth of firmicutes is transferred to the baby anaerobically
promotes growth of bifidobacteria
Following fermentation of carbohydrate monomers, the short-chain fatty acid _____ travels to the liver where it inhibits cholesterol synthesis. acetate lactate butyrate propionate
propionate
Classifying certain probiotics as drugs has the consequence of _____. requiring pure cultures with sequenced genomes creating competition among probiotic producers requiring safety and efficacy clinical trials requiring that they be available only by prescription
requiring safety and efficacy clinical trials
Immune cell maturation requires _____ produced by the gut microbiota as well as cytokines released by intestinal immune cells. MAMPs short chain fatty acids secondary bile salts amphipathic peptides
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 _____. ethanol (alcohol) short-chain fatty acids lactate hydrogen and CO2
short-chain fatty acids
Foods or supplements that include both live microorganisms, which when administered in adequate amounts confer a health benefit to the host, and compounds to enhance the colonization of the GI tract are termed _____. probiotics prebiotics synbiotics
synbiotics
Microcins and colicins can inhibit which three of the following? tRNA synthetase cell wall synthesis nitrogen fixation RNA polymerase topoisomerases detoxifying reactive oxygen species
tRNA synthetase cell wall synthesis RNA polymerase
In the gut, the growth of anaerobes is favored over facultative anaerobes by _____. colicin production microcin production the low oxygen tension sensitivity to killing by C-type lectins
the low oxygen tension
The metabolome is best described as _____. the metabolic products secreted by bacteria host biochemicals and hormones that affect the gut microbiome metabolism host biochemicals and hormones that affect the composition of the functional core microbiome
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 pathogens cannot establish themselves in the gut in the presence of antibiotics once the gut microbiome is established in an infant, it cannot be changed substantively
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 _____. hospital workers the hospital environment their mother microbes in the air
their mother
Animals that eat a meat-intensive diet introduce L-carnitine and phosphatidylcholine to their GI tract, where microbial metabolism converts them to _____. reactive oxygen species trimethylamine serotonin amino acids
trimethylamine
Some Gram-negative bacteria deliver bacteriocidal toxins directly through the cell envelope of competing bacteria through their _____. membrane vesicles type VI secretion system conjugative pili type III secretion system
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 enlarged absent cancerous
underdeveloped
Select all that apply In addition to bacteria, which three of the following are also present in the human microbiome? water molds viruses archaea algae fungi viroids
viruses archaea fungi
Mucosal tolerance explains how _____. we can host many microbes and foreign food antigens in our gut without responding with an overwhelming inflammatory response the microbiota in the gut is protected from disease by the presence of a healthy community the microbiota in the gut is at least partially responsible for the development of the innate immune system
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. stem white blood red blood B
white blood