2. Sections covered (overview)
30.1 microbial interactions
30.2 human microbe interactions
30.3 normal microbiota of the human
body
3. Chapter objectives
After reading this chapter, the student should be able to:
discuss the term symbiosis as it relates to microorganisms, and
give examples of the theme areas mentioned above by
describing the various interactions of microorganisms with
one another and with nonmicrobial members of ecosystems
describe examples of symbiosis in microorganisms found in
extreme environments
describe gnotobiotic animals and their importance in
understanding the roles of microorganisms in higher organisms
describe the body sites where normal microbiota are found
and give examples of the microorganisms found there
4. Microbial Interactions -
terminology
physical associations
ectosymbiont
organism located _on surface
_ another organism (usually larger)
endosymbiont
organism located within another organism
there are also examples of hosts that have
more than one symbiont associated with it:
consortium
physical association of two or more different organisms,
usually beneficial to all
Two dif
ectosym
found o
On red
and in t
the e sm
subarin
Grows o
is exam
nanoba
has nev
one,
Endosy
another
ritizia in
hydroth
endosy
and pro
Consort
associa
when th
benefita
5. Basic characteristics of
symbiotic relationships
that occur between
different organisms
Basic c
symbio
occur b
organis
Symbio
mean p
Diagram
relation
relation
benefic
But if w
amensa
relation
one par
6. Mutualism
some __________ to both partners
relationship with some degree of
obligation
often partners cannot live separately
mutualist and host are dependent on
each other
8. Sulfide-based
mutualisms:
Hydrothermal Vents
and Related
Geological Activity
Vent fluids are anoxic and contain hydrogen
sulfide. They can reach a T of 350oC, but the
water does not boil. Surrounding water has
lower T.
hin
ity
ean
ut fluid
s
ssure
close
erma
d
H2S
don
new
elec
ene
We
wate
cold
Sulf
in th
Moc
sou
ene
mes
able
tem
The
high
prop
sou
elec
9. Tube Worm-Bacterial
Relationships
exist thousands of meters
below ocean surface near
vents
chemolithotrophic bacterial
endosymbionts live within
a specialized organ
(trophosome) of host tube
worm c,
fix CO2 with electrons
provided by H2S
Symbiotic chemolithotrophic bacteria within
the symbiont-containing region of the body
wall of a marine worm, visualized with FISH
and fluorescent microscopy. Bar=10 µm
c
an
s
ey
S as
e
c
10. Tube worm-
bacterial
relationships
Riftia pachyptila (Tube worm, Galapagos hydrothermal vent site, 2,550 m), 1 m x 20 cm.
Hydrogen sulfide absorbed through the gill plume is bound to the worm’s hemoglobin
and oxidized by endosymbiont bacteria.
http://www.youtube.com/watch?v=XotF9fzo4Vo
Riftia’s blood contains
unique hemoglobin which
captures hydrogen sulfide
and oxygen from seawater
in the trophosome packed
with chemolithotrophs
Endosymbionts fix CO2 (from blood
stream, hemoglobin and
decarboxylation of e.g. malate and
succinate) using e’s from H2S.
Some of the resulting C is
transferred to the host.
ce organic
hrough
of energy
n in the
orm new
s at the
Chemos
can be u
mutualis
there is
worm an
worm co
( bcs it c
concent
water)
two way
11. Review questions – pg. 722
How could you test if an insect-microbe
relationship is mutualistic?
What is the critical characteristic of a
mutualistic relationship?
What is the role of Riftia hemoglobin in the
tube worm – endosymbiont relationship?
How is the Riftia endosymbiont similar to
cyanobacteria and how is it different?
13. Cooperation
along with commensalism is a positive, but not
obligate form of symbiosis which may involve
syntrophic relationships (“together-nourishment”)
benefits both organisms in relationship
syntrophism
growth of one organism depends on or is improved by
growth factors, nutrients, or substrates provided by
another organism growing nearby; sometimes both
benefit
Both partners can b
14. OM =
organic
material
Selected Examples of
Cooperative Symbiosis
Chromatium oxidizes sulfide
to sulfate and provides
organic matter and electron
acceptor to Desulfovibrio
Azotobacter uses glucose
provided by Cellulomonas
and in turn provides fixed
nitrogen
in
Not mutua
obligate P
dependen
by organis
partner
Found in
fixes pla
benefitte
celulomo
cellulose
15. Review questions – pg. 724
How does cooperation differ from
mutualism
What is syntrophism? Is physical
contact required for this type of a
relationship – why or why not?
17. Commensalism
one organism Benefits_and the other (host) is
Not harmed
Commensal (lat. “together” & “table”)
organism that benefits
Not directly dependant, can survive separated
from host
often syntrophic, e.g. products produced
improve growth
can also involve modification of environment
by one organism, making it more suited for
another organism
e.g.: synthesis of acidic waste
products during fermentation
stimulates proliferation of acid-
tolerant microorganisms
18. An Example of
Commensalis
m
nitrification
NH3→NO2 →NO3
carried out by two different
bacteria
e.g., Nitrosomonas carries out
first step
e.g., Nitrobacter carries out
second step (i.e., it benefits
from its association with
Nitrosomonas)
FISH-based identification of ammonia-
(blue) and nitrite-(red) oxidizing bacteria.
ical for
19. More Examples
microbial succession during spoilage of milk
fermentative bacteria produce acids that promote
growth of acid tolerant species
skin or surface microbes on plants or animals
host plant or animal releases volatile, soluble, and
particulate organic compounds, which are used by
commensals
20. Review questions – pg. 724
How does commensalism differ from
cooperation?
Why is nitrification a good example of
commensalism?
21.
22. Predation
among microbes, predation involves a
predator species that attacks, usually
killing its prey
Describes relationship by one bacteria attacks and kills other
bacteria or prey, one directional relationship and negative
concequences
23. Microbial Predators
Bdellovibrio penetrates cell wall,
grows outside plasma membrane
http://www.youtube.com/watch?v=-uZjo0ohjFw
Vampirococcus epibiotic mode of
attacking prey, degradative
enzymes
Daptobacter penetrates prey then
directly consumes the cytoplasmic
contents
gs
ut inside
causes
24.
25. Parasitism
one organism gains parasite) and the other Is
harmsed (host)
always some co-existence between host and
parasite
successful parasites have evolved to co-exist
in equilibrium with their hosts
if balance upset, host or parasite may die
ween parasite
26. Balance Between Host and
Parasite
Example – Typhus
Rickettsia typhi is causative agent
harbored in fleas, lives on rats
transmitted to humans by flea bites
is endemic within population until societal
changes, e.g., war or other disruptions
occur, and then becomes epidemic
Exists in equlibrium n
completely until equi
changes in lifestlye o
host spreads infectio
epidemic
27. Another Example
lichens, an example of a controlled parasitism
association only occurs when organisms are
nutritionally deprived
mycobiont
fungal partner
provides water, minerals, sheltered environment
and firm substratum for growth
phycobiont
alga or cyanobacterium
provides organic carbon and oxygen
Algea and fungus contr
parasitism
Demonstrated in lichen
28. lichens – associations of ascomycetes (mycobiont) and
photosynthetic bacteria (phycobiont)
•Question: why is this
NOT classified as a
mutualistic
relationship?
“Controlled parasitism”:
some phycobiotic
cyanobacteria and algae grow
more quickly when cultured
alone
Lichens
building
29. Genomic Reduction
outcome of long-term parasitic
relationship
parasite loses unused genomic
information and can survive only in
association with the host
Example? Obligate intracellular
bacteria, e.g. Rickettsia –
grow in vertebrate
erythrocytes, macrophages,
vascular endothelial cells,
depend on host for ATP
de host,
site
uces size
wed as loss
site doesn’t
o make
ause its
provides
monia, bcs
o make it it
his
ore
30.
31. Amensalism
Negative impact of one organism on another based
on release of a specific compound
some examples
Antibiotic production by fungi and bacteria
use of antibiotic-producing streptomycin by ants to control
fungal parasites
production of antibacterial peptides by insects and mammals
e.g., cecropins, defensins, and athelicidins
Production of a
or bacteria, an
microorgs so th
an advantage
producing stra
Ex streptomyc
32.
33. Competition
occurs when two organisms try to
acquire or use the same resource
Nutrients electron
etc
34. Two Possible Outcomes of
Competition
one organism dominates
competitive exclusion principle
two organisms overlap too much in their
resource use, and one population is
excluded(e.g. slower growers)
two organisms share the resource
both survive at lower population levels
Fast vs slo
would outc
reduce nu
one micro
one micro
would be r
35. Review questions – pg. 726,
728
What is the competitive exclusion principle
and where is this principle demonstrated in
the natural world?
How are predation and parasitism similar
and different?
Discuss the relationship within lichens
36. Test your knowledge
Mutualism is
A. mutualist depentand on host
B recipricol benefit both partners
C. partners will not survive separately in
many cases
D. all of the above….
37. T YOUR KNOWLEDGE
In commensalism
A. host and commensal can be
separated and remain viable
B. the commensal is metabolically
dependent on the host
C. host provides some factor that
commensal cannot get otherwise
38. Section 30.2: Human-Microbe
Interactions
the human body is a diverse
environment
specific niches are present
More microbial cells or human cells?
ecological principles apply to the many
interactions that occur between the host
and its normal microbial flora
Microbial flora, microbiota, microbiome
Body consists o
or human cells,
1014
Interactions betw
microflora these
and influence he
host,
39. Human-Microbe Interactions
Microbial flora, microbiota, microbiome
microbiome
All the genes of the host and the
microbiota composite genetic
background
goal is to determine the impact that
microbial gene function has on human
health (our genes do not encode the
products needed for all biological functions
of the human body)
40. Human-Microbe Interactions
e.g. some human traits (obesity?) may be influenced by bacteria
(Firmicutes vs. Bacteroidetes?)
•greater gene activation for proteins that catabolize complex
carbohydrates more energy
•trigger genes that slow host metabolism
colon and
ans that
st
o be
extract
st
41. Human-Microbe Interactions
pathogenicity
ability to produce pathological change or
disease
pathogen
any disease-producing microorganism
Tolerating a normal microbiota suggests that the host derives benefit (e.g. viamin K
produced by fecal coliforms
Microbial niches are defined by cellular receptors, surface properties, secreted
products, etc….
Host defense prevent microbes from establishing a parasitic or pathogenic
relationship
42. 27.3: Normal Microbiota of the
Human Body
normal microbiota
Microbes regularly found at an anatomical
site that contacts the external enviornemnt
( brain, blood, muscles)
Internal tissues are normally freee of
microbes
Lifelong symbiotic relationship begins at birth
(colonization of newborn depends on
environment – e.g. breast fed infants)
43. Reasons to Study Normal
Human Microbiota
to gain insight into possible infections resulting from
injury ( if we know who is there)
to understand causes and consequences of
overgrowth of microbes normally abesent from body
site
To increase awareness of role played by indegenous
microbe in stimulating immune response
http://www.youtube.com/watch?v=vfYN3-xX_8M&feature=related
http://www.youtube.com/watch?v=LfeNTQxxn0w
44. Interactions Between a Host
and Its Normal Flora
interactions include a broad
range of symbiotic
interactions including
commensalism
mutualism
parasitism
examples of both ecto- and
endosymbiotic relationships
are present in the host
es
46. Skin – 2m2
commensal microbes include both resident (grow on
skin) and transient (temporally present) microbiota
mechanically strong barrier
inhospitable environment
Sligthly acidic pH
______________high conc of NaCl________
______________many areas low in moisture________
________shedding_________________
inhibitory substances excreted by sweat glands (e.g.,
lysozyme, cathelicidins – antimicrobial peptides)
most skin bacteria are found on superficial cells,
colonize dead cells, or are closely associated with oil
and sweat glands (many different phyla + yeast)
y be
me
eat
nd
n live
47. Acne Vulgaris
caused in part by activities of
Propionibacterium acnes
Lipids fluid secreted by oil glands, hormonal
activity provide a hospitable environment for P.
acnes
Change lipids to unsaturated fatty acids (volatile,
odiferous, active against gram-negative bacteria)
inflammatory response
Changes lipid compo
fatty acids and they a
causes body odor to
acne
She wants us to r
bacteria and know
comes from Propio
Also used for cheese
48. Nose and Nasopharynx
Staphylococcus aureus and S. epidermidis
predominant bacteria present
found just inside nostrils
Also on skin of the face
nasopharynx (above the soft palate) may
contain low numbers of potentially pathogenic
microbes
e.g., Streptococcus pneumoniae, Neisseria
meningitidis, and Haemophilus influenzae
49. Respiratory Tract
Upper and lower respiratory tracts have
no normal microbiota
microbes moved by:
continuous stream of mucus generated by
ciliated epithelial cells
phagocytic action of alveolar macrophages
lysozyme in mucus
Body generates mucus
microorgs
Mucus contains macrop
microbial microorgs
50. Eye
from birth throughout a human life,
small numbers of bacterial commensals
are found on the conjunctiva of the eye
the predominant bacterium is
Staphylococcus epidermidis (also S.
aureus, Haemophilus, S. pneumoniae)
s by bact on moist
51. Mouth
Favourable environmennt – water, nutrients, pH
contains organisms that survive mechanical removal
by adhering to gums and teeth
contribute to formation of ____________, dental caries,
gingivitis, and periodontal disease
Those that cannot attach are removed by mechanical
flushing to the stomach
Shedding of epithelial cells removes microorganisms
ce
s
soft
emnt
has
s
f
ory
ffect
53. Colonized soon after birth by Streptococcus, Neisseria, Actinomyces,
Veillonella (lactate fermenter), Lactobacillus, yeasts (aerobes and
obligate anaerobes)
First teeth – anaerobes Porphyromonas, Prevotella (Bacteroidetes),
Fusibacterium (Fusobacteria)
Streptococcus parasanguis, S. mutans -enamel
surfaces
S. salivarius –buccal (the side of a tooth that is
adjacent to the inside of the cheek) and gingival
epithelium, saliva
Produce a glycocalyx and adherence factors that
allow them to attach to surfaces
These microor
Anarobic niche
formed and su
growth for a he
need some of
anaerobic bact
important to ke
microorgs colo
brushing becau
food remains in
and produce a
54. Caries (enamel
damage due to acid
formation)
Gingivitis (gums)
Periodontal disease
(gums, bone)
http://www.textbookofbacterio
logy.net/normalflora_5.html
55. Stomach
most microbes killed by acidic conditions (pH
2-3)
some survive if pass through stomach very quickly
(less than 10 cells/ml gastric fluid: e.g.
Streptococcus, Staphylococcus, Lactobacillus,
yeasts)
some can survive if ingested in food particles
Helicobacter pylori
http://www.youtube.com/watch?v=u244Hwu51Hw
t and are coated in
H, and pH os neutral in
Microorg
they are
content b
survive a
through
able to b
or they c
food, if fo
exposed
enviorne
helicoba
epithelia
surface P
epithelia
to neutril
bact eats
nutrients
mucus a
cause of
associat
cancer
56. Small Intestine
divided into three areas
duodenum
contains _few organisms (acidic juices, bile, pancreatic
secretions; gram positives, enterococci, lactobacilli,
Candida)
jejunum
Enterococcus, yeasts, lactobacilli
ileum
flora present becoming similar to that in colon
pH becomes more alkaline enterobacteria, anaerobic
gram negatives
Thre areas, all thr
bacteria, and yea
57. Large Intestine (Colon)
largest microbial population of body, over 400
different species isolated from feces, 1012
organisms/g
Anaerobic gram negatives, gram positive rods,
Candida, protozoa, uncultivated
eliminated from body by peristalsis, desquamation, and
movement of mucus
replaced rapidly because of their high reproductive rate
most of the microbes present are anaerobes
Disruptive factors change intestinal microbiota (stress,
altitude changes, parasites, antibiotics)
Bacteroides thetaoitamocrion
colonizes exfoliates host cells, food particles and
sloughed mucus
Anaerobic because ther
anaerbes found here to
There are now many mi
diversity many diff spec
present, these microorg
epithelial cells coated in
filled,
Can be attached to food
digestions of food partic
Microorgs benefit host b
microorgs synthesize nu
help bread down food, m
because they get protec
Overgrowth of pathogen
58. Genitourinary Tract
kidneys, ureters, and bladder
normally free of microbes
distal portions of urethra
few microbes found (S. epidermidis, E. faecalis,
Corynebacterium)
female genital tract
complex microbiota in a state of flux due to
menstrual cycle
acid-tolerant lactobacilli predominate pH 4.4.-
4.6 inhibitory to other organisms
If they have that me
59. The Relationship Between
Normal Microbiota and the Host
Usually mutually beneficial
normal microbiota often prevent colonization by pathogens
bacterial products, e.g., vitamins B and K are beneficial to the host
Harmless or beneficial in their normal location and in the absence of
abnormalities, in foreign locations or in compromized hosts
diseases
opportunistic pathogens
members of normal microbiota that produce disease under certain
circumstances; pathogens are prevented from causing disease by
competition by normal microbiota (e.g. low pH prevents colonization by
yeast)
compromised host
debilitated host with lowered resistance to infection (due to diabetes,
malnutrition, cancer, etc.) e,g, bacteroides (large intestine) in
peritoneal cavity or pelvic tissues bacteremia
“Everything is everywhere: but the environment selects” ?
Co
inte
inv
sec
tran
stre
hea
mic
and
mu
Op
cha
mic
Lea
env
pat
and
occ
tryi
don’t want too much because overgrowth
of good microorgs because produce acidic
60. Test your knowlegse
Microorgs commonly associate with
human body are called
normal microbial flora or the
normal microbiota
Microbiota describes microorgs that colonize
body, and the microbiome is the study of
genes of the microbiota that makes up the
human body use structural genes to obtain
info abot taxonomic relationships
61. Test your knowledge
A pathogen is any disease producing
microorg
A species bacter associated with oil
glands of skin
A. staphylococcus
b. pityrosporum
c.propionibacterium
62. Tyour knowledge
When members of normal microbiota of
human body bcm pathogenic and
produce disease they are called
pathogens
D. opportunistic
Ex strep in the mouth, c. diff in the intestine
63. Review questions – pg. 730,
733, 736
Why is the skin usually not a favorable microenvironment for
colonization by bacteria?
How do microorganisms contribute to body odor?
What are the most common microorgansism found in various body
sites?
Why is the colon considered a large fermentation vessel?
What physiological processes move the microbiota through the
gastrointestinal tract?
Explain how the principle of competitive exclusion is used by normal
host microbiota in preventing the establishment of pathogens
What is the difference between an opportunistic microorganism and a
pathogen?
64. Diff btwn oppertunistic pathogen and a
pathogen?
Why is colon considered large
fermentation vessel
Bcs anaerobic environment and they do
fermentation in the absence of oxygen
65. Critical thinking review
questions
Describe an experimental approach to
determine if a plant-associated microbe is
commensal or mutualistic?
Why do some patients who take antibiotics
for acne develop yeast infections of the
mouth or genital-urinary tract?
