BIOL 224 Lecture 2: Microbes- Friends or Foe
January 14th 2020
BIOL 224- Introduction to Medical Microbiology
Learning objectives:
• Microorganisms- microbes
• Pathogens- opportunistic and primary
• Lethal and infectious dose
• Stage of pathogenesis
Common Perceptions of Microbes
• They are very bad
o Cholera
o Leprosy
o Necrotizing fasciitis
What are Microbes?
• Microbes
o Most are microscopic
o Tiny living things
o Need a specific magnification to see microbes
o Human eyes can see 100 micrometers
o Phylogenetic diverse
▪ Radiated into a diverse set of lineages
o Not all microbes are the same- they come from all different kinds of domains
o Metabolic diverse thrive in inhospitable environments
o Many are beneficial and some have tremendous commercial value
▪ Includes: biofuel, food industry, pharmaceutical industry
o Countless live with us in a symbiotic relationship
▪ Many microbes live in our gut
Microbiota and Microbiome
, • Microbiota is a collection of microbes colonizing our bodies without normally causing
disease
o Variations across different body sites (colonization sites)
o Changes throughout life
▪ After looking at gut microbiota throughout human life, you can see
differences in what bacteria is in the gut based on health, and what you
are fed as a child, as well as age
o Microbiota shape us
▪ Maternal obesity- long-term disease risk
▪ Nothing stays constant
o Linkage to metabolic diseases such as obesity, diabetes type II and even
Alzheimer and Atherosclerosis can be linked to impairment of microbiota
o Different acidities and pH affect the types of microbes that a human is hosting
• Resident microbiota
o Part of the normal microbiota throughout life
o Mostly commensal
o E. coli is a resident microbiota that gives our body vitamin K
• Transient microbiota
o Remain in/on the body for short period
▪ Competition from other microorganisms
▪ Elimination by the body’s defense cells
o Salmonella is a transient microbiota and will try to settle, but as long as you are
healthy, the body will flush them out
• Microbiome is the total number of microbial genomes in a defined environment
• Humans are more microbes than they are eukaryotic (more microbes than DNA)
Host- Microbe Interactions
• Mutualism or syntropy
o All members benefit from this relationship
▪ Example: intestinal bacteria
• Commensalism
o One member benefits, other is unaffected
▪ Example: fact mites
• Amensalism
o One member benefits, one member unaffected
▪ Example: fungus secreted antibiotics and inhibit surrounding bacteria
• Parasitism
o One member benefits, one member harmed
▪ Example: Giardia intestinalis causing giardiasis
January 14th 2020
BIOL 224- Introduction to Medical Microbiology
Learning objectives:
• Microorganisms- microbes
• Pathogens- opportunistic and primary
• Lethal and infectious dose
• Stage of pathogenesis
Common Perceptions of Microbes
• They are very bad
o Cholera
o Leprosy
o Necrotizing fasciitis
What are Microbes?
• Microbes
o Most are microscopic
o Tiny living things
o Need a specific magnification to see microbes
o Human eyes can see 100 micrometers
o Phylogenetic diverse
▪ Radiated into a diverse set of lineages
o Not all microbes are the same- they come from all different kinds of domains
o Metabolic diverse thrive in inhospitable environments
o Many are beneficial and some have tremendous commercial value
▪ Includes: biofuel, food industry, pharmaceutical industry
o Countless live with us in a symbiotic relationship
▪ Many microbes live in our gut
Microbiota and Microbiome
, • Microbiota is a collection of microbes colonizing our bodies without normally causing
disease
o Variations across different body sites (colonization sites)
o Changes throughout life
▪ After looking at gut microbiota throughout human life, you can see
differences in what bacteria is in the gut based on health, and what you
are fed as a child, as well as age
o Microbiota shape us
▪ Maternal obesity- long-term disease risk
▪ Nothing stays constant
o Linkage to metabolic diseases such as obesity, diabetes type II and even
Alzheimer and Atherosclerosis can be linked to impairment of microbiota
o Different acidities and pH affect the types of microbes that a human is hosting
• Resident microbiota
o Part of the normal microbiota throughout life
o Mostly commensal
o E. coli is a resident microbiota that gives our body vitamin K
• Transient microbiota
o Remain in/on the body for short period
▪ Competition from other microorganisms
▪ Elimination by the body’s defense cells
o Salmonella is a transient microbiota and will try to settle, but as long as you are
healthy, the body will flush them out
• Microbiome is the total number of microbial genomes in a defined environment
• Humans are more microbes than they are eukaryotic (more microbes than DNA)
Host- Microbe Interactions
• Mutualism or syntropy
o All members benefit from this relationship
▪ Example: intestinal bacteria
• Commensalism
o One member benefits, other is unaffected
▪ Example: fact mites
• Amensalism
o One member benefits, one member unaffected
▪ Example: fungus secreted antibiotics and inhibit surrounding bacteria
• Parasitism
o One member benefits, one member harmed
▪ Example: Giardia intestinalis causing giardiasis
