Chapter 27/33: Microbial Interactions

Symbiosis:

a symbiotic relationship between two organisms

Ectosymbiont is:

the organism located ON the surface

Endosymbiont is:

the organism located within another

Ecto means:

outside; on surface

Endo means:

inside; inside another organism

Consortium

a host with more than one associated symbiont

Consortium relationships are permanent, T or F?

False; can also be intermittent or cyclic

If a pathogen is permanent, what is the outcome of the host?

Death

How many types of microbial interactions are there? What are they?

7

-Mutualism

-Cooperation

-Commensalism

-Predation

-Parasitism

-Amensalism

-Competition

What are the positive microbial interactions?

Mutualism, cooperation, commensalism

What are the negative microbial interactions?

Predation, parasitism, amensalism, competition

In mutualism, what is the relationship between the host and microbe?

they depend on one another; one will die w/o the other

In mutualism, there is a benefit to both partners but there is no obligation to one another, T or F?

false; they need each other to survive; there is a degree of necessity

An example of mutualism is microorganism-insect relationship between aphids and B. aphidicola. Why is this?

they have coevolved; there is genome reduction where the aphids stopped making necessary proteins/amino acids b/c the bacteria provides them and vice versa; now they both need each other

Another example of mutualism is the protozoan-termite relationship between termites and Trichonympha. Why is this?

termites cannot break down the sugar found in wood (lignocellulose) but Trichonympha can. The termite provides food for the protozoan and the protozoan helps break down the food needed for the termite to survive; another case of genomic reduction

In cooperation, what is the relationship between the host and microbe?

a positive symbiosis that benefits both partners but it is NOT obligatory, meaning one can leave and they both will survive on their own

An example of a cooperation relationship is bacteria and nematodes. Why is this?

X. nematophila (bacteria) live in S. carpocapsae (nematode) gut;; S. carpocapsae will infect an insect (usually a butterfly) and once nematode starts feeding on it, bacteria will be released from the gut of nematode and produce molecules that kill the insect; The nematode will then produce compounds that will prevent other microorganisms from consuming the insect cadaver; Nematode will use insect corpse as a nutrient source to reproduce and the bacteria will colonize juveniles before they emerge.

What is commensalism?

A relationship in which one organism benefits and the other is neither helped nor harmed

Is commensalism positive or negative?

positive

Commensalism is also known as a ____ relationship

unidirectional

Commensalism is often ____, or also known as cross-feeding. What does this mean?

Syntrophic; means that there is a modification of the environment; 1 microbe is changing environment due to the waste it is making/producing

What is an example(s) of commensalism?

1) Nitrification (NH3-->NO2-->NO3); first step is nitrosomas, the waste is eaten by nitrobacter (second step)

2) Spoilage of milk: milk is NOT sterile it is pasteurized, so there are always bacteria present in milk. Bacteria will produce waste, then that waste is eaten by another bacteria, etc etc; this is what causes curding.

3) Formation of biofilms

4) Skin or surface microbes on plants or animals

What is predation? Is it a positive or negative relationship?

predation is where the microbe will kill the host and obtain biochemical precursors and energy after the prey is dead; it is a negative relationship

What are the four major microbes that partake in predation?

-Bdellovibrio

-Vampirtococcus

-Daptobacter

-Mycoxoccus

What is Bdellovibrio? What shape is it? What does it do to the prey?

a bacteria that is vibrio shaped; will penetrate cell wall and grows outside the plasma membrane; it will replicate inside the periplasmic space, and will not break the peptidoglycan until the prey is no longer needed, and will break the membrane, killing the prey

The area between the cell membrane and the cell wall is called the:

periplasmic space

What is Vampirococcus? What shape is it? What does it do to the prey?

a bacteria that is cocci shaped; uses a epibiotic (leeches off) mode of attacking the prey; stays outside (ecto) the prey and will bind and absorb nutrients, eventually killing the bacteria

What is Daptobacter? What does it do to the prey?

is a bacteria; will penetrate the prey then directly consume the cytoplasmic contents; it is "endo" means it is found inside

Myxococcus is a fungi, T or F?

false; it is a bacteria

What is Myxococcus? What shape is it? What does it do to prey?

a bacteria that is cocci shaped; considered a "wolf pack" type f predator; cells use gliding motility to creep, overtake prey, and release degradative enzymes

Where is the gliding motility found in Myxococcus?

slime layer

Myxococcus is known to be what kind of predator?

facultative predator

What does facultative predator means?

means that the predator will either kill the prey or they won't if not needed.

Why is Myxococcus bacteria named with the prefix myxo-

b/c the bacteria has aerial hyphae, similar to that of fungi

What bacteria is Myxcoccus known to kill?

E. coli

What is parasitism? Is it a positive or negative relationship?

a relationship where one organism gains (parasite) and the other is harmed (host); it is a negative relationship

Parasitism will end up with the host dead, T or F?

false; the parasite will not kill the host; will only take what it needs

In terms of evolution, what have parasites gone through?

genomic reduction; it stop making what is needed for survival and now needs a host to provide what it needed to survive

When do parasite obtain biochemical precursors?

While the host is still alive; does not kill it like seen in predation relationships

Successful parasites have evolved to co-exist in:

equilibrium

What is amensalism? Is it positive or negative?

Where one organism harms another due to the release of a compound

What are two examples of amensalism?

-antibiotic production

-bacteriocin production

What do antibiotic production do?

kills those who do NOT look like them

What does bacteriocin production do?

kills those who DO look like them

In bacteriocin production, since it is killing others that look like itself, it will eventually kill itself, T or F>?

false; will not kill itself

What is an example of antibiotic production?

Penicillin; penicillin comes from penicillium which is a fungus; penicillin kills bacteria, which is why it is called an antibiotic

What plate is used to test antibiotics?

Kirby-Bauer

What is the clearing called around the antibiotic disc?

Zone of Inhibition

The bigger the zone of inhibition, the better the antibiotic, T or F?

False; does mean better; you need to look at the chart with the diameter sizes for each antibiotic as they are all going to produce different results/ranges

What is compeition? Is it negative or positive

occurs when two organisms try to acquire or use the same resource; it is negative

What are the two possible outcomes with competition?

-one organism dominates

-two organisms share the resource

Humans are known as ___ for microbes

incubators

Humans have more microbes present that they do cells, T or F?

true

What is microbiome?

the microorganisms in a particular environment (including the body or a part of the body).

Microbiome is also known as:

normal microbiota, normal flora

What are superorganisms?

where gene-encoded metabolic processes of the host become integrated with those of the microbes; example: we do not make amino acids on our own, we need microbes to do this for us!

We all have/start off with the same microbiome, T or F?

false; it is unique to every single living thing

Microbiomes stay the same throughout life, T or F?

false; it is dynamic which means it is always changing

Why do microbiomes change?

can be reasons such as diet, age, genetics, what vaccines one has gotten, infection, antibiotic taken, seasons, etc.

E. coli and streptococci help make what kind of environment in the gut?

reducing

Since E. coli and streptococci make a reducing environment in the gut, this enhances the growth of:

bifidobacteria

What is something mammals (particularly humans) that helps select for non-pathogenic bacteria?

milk

There are two hypothesis on how one obtains their microbiome. What are they?

1) We are born sterile and our biome starts accumulating the moment we are born

2) Microbiome starts in the womb

What is bifidobacteria?

a good bacteria that is found in many probiotics; found in breastfed babies

What can bifidobacteria do?

synthesize all amino acids

Bifidobacteria is ___trophic

prototrophic

Bifidobacteria can do fermentation. What does this mean for us>

will lower pH levels in the gut, making it more acidic; inhibits pathogens from growing

Germfree animals are known as:

Gnotobiotic

What is the purpose of germfree animals?

To study the effects of microbes; compares germfree animals and normal animals with a microbiome

If a single microbe were introduced to a germfree animal and a normal animals, which one is most likely to die first? Why?

germfree animal will die first b/c it does not have an innate immunity

Germ free animal develop different than normal animals, T or F? Explain.

true

-does not have the same immune system as an animal with a microbiome

-does not undergo the same brain development

-does not have the same motor skills

When was the Human Microbiome Project initiated and by who?

initiated in December 2007 by the National Institutes of Health (NIH)

As of 2014, the Human Microbiome Project has done:

-whole metagenomic sequencing data for around 800 healthy human cohort samples obtained

-16S sequence data from around 5,000 healthy human cohort samples

What are the five main phyla of bacteria present in most humans? Are these phylas present in the same amount in everyone or different?

-Actinobacteria

-Bacteroidetes

-Firmicutes

-Fusobacteria

-Proteobacteria

found in different % depending on age and other factors

What kind of microbiota is seen on skin?

resistant and transient

What kind of environment is found on skin?

inhospitable; high concentration if NaCl, slightly acidic pH, many areas low in moisture

What kind of bacteria can be found on skin due to its halophile tendencies?

S. epidermidis

What kinds of inhibitory substances are found in the microbiota of the skin?

-lysozymes and cathelicidins

-oleic acid by gram positive C. acnes

These inhibitory substances re part of innate or adaptive immunity?

innate

What do lysozymes do?

break the beta 1,4-glycosidic bonds of bacteria

Cathelicidins are released by:

macrophages and granulocytes

macrophages and granulocytes are:

White blood cells; part of leukocytes

Cathelicidins cause harm to:

the cell membrane of pathogens

Cathelicidins are part of innate or adaptive immunity?

innate

Oleic acid inhibits what kind of bacteria?

gram-negative

Acne vulgaris is caused in part by what bacteria/

Cutibacterium (formerly known as Propionibacterium) acnes

Cutibacterium causes the buildup of:

sebum; sebum accumulation

Cutibacterium prefers what kind of environment?

oily; moist environments

What kind of pathogen is Cutibacterium? Why?

opportunistic pathogen; b/c the fermentation pathway it uses is different

Deodorants for the skin have?

antibacterials

Where/why do odors form on skin?

due to the fermentation of bacteria on skin

Eyes should be sterile but they are not. Why? What is found near/on the eye?

Due to the skin surrounding the eye; there is a small # of commensal bacteria found in the conjunctiva of eye

What is the most common bacteria found near/on eye? Why?

S. epidermidis; b/c of surrounding skin

Puffy red eye means:

allergies

Red eyes with tears means:

viral infection

red eyes with yellow discharge means:

bacterial infection

the external ear has a similar flora as:

the skin

Along with bacteria, what else can one find on the external ear?

fungi

What kind of fungi can be found on the external ear? What is unique about it?

C. auris; this fungi can stay on surfaces for a very long time and have the opportunity to become systemic, which can be deadly

C. auris is nosocomial, which means it is typically found:

in hospital settings