ANSWERS WITH COMPLETE SOLUTIONS VERIFIED
microbiota vs microbiome
microbiota - organisms
microbiome - organisms + genes + genome
The gut microbiota contains more than __ cells
more than __ species
200 trillion cells
>1000 species
The microbiome contains __x the cells in the human body
The gut microbiome is __x larger than the human genome
10x cells
150x genome
Who came up with the official definition of microbiota?
Lederberg and McCray, 2001
Microbiota definition
"Ecological community of commensal, symbiotic, and pathogenic microorganisms within
a body space or other environment"
True/False the microbiome is generally non-pathogenic and beneficial to the host
true
Transient microbiota
,microbes that are present for various periods and then disappear
Although these types of organisms may colonize a host and reproduce briefly, the
defenses of the body do not allow them to become permanent.
3 types of Symbiosis
mutualism, commensalism, parasitism
Commensalism
one organism benefits the other and the other is unaffected (ex: mycobacteria in the
ear)
mutualism
both organisms benefit (ex: E. coli in the colon, synthesizes vit K)
parasitism
one benefits at the expense of the other (ex: disease causing bacteria)
___ plays a fundamental role in immune maturation - complete absence of
bacteria in the gut results in ___ and low levels of ____
mutualism
results in gut-associated mesenteric lymph tissue
low levels IgA
Specific functions of the microbiota
seal body spaces, mitigate intestinal pathogens, maintain tissue homeostasis, facilitate
fermentation of dietary fiber (pectin, etc), critical energy yield, metabolic end products
, and therapeutic drug processing, signaling among cells and organ systems (butyrate -
energy for gut epithelial cells; acetate and propionate - lipogenesis and
methods to study the microbiota
16S rRNA gene sequencing-based surveys and shotgun metagenomic approach
16S rRNA gene sequencing-based surveys
Gene contains highly conserved regions and variable regions
amplify 16S rRNA genes using primers directed at conserved regions but flanking
variable regions
align gene sequences, resolve phylogenetic relationships at different depths
Most 16S rRNA sequences come from previously ____
undescribed microbes
Operational Taxonomic Units
a definition used to classify groups of closely related individuals
Sequences are clustered according to their similarity to one another
OTUs are defined based on the similarity threshold (about 97% similarity)
limitations of 16S rRNA gene based analysis
Many genomes have miltuple and nearly-identical copies of the 16S rRNA operons
Not always possible to accurately normalize 16S data
Cannot always obtain accurate estimates of diversity and abundance
Strain-level resolution of the microbial community is not always possible
Strains of the same species can have different phenotypes and functional capabilities
not possible to accurately infer or reconstruct functional and metabolic capabilities