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Chapter 30
Microbial Interactions
Sections covered (overview)
30.1 microbial interactions 30.2 human microbe interactions 30.3 normal microbiota of the
human body
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
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 diff types of symbiants, ectosymbiotic relationships microorg found on surface
On red dots surrounding green dots, and in the electron microscopic pic it is the e small archae it inhibits hot subarine vents
Grows only symbiotic with green , this is example of ectosymbiotic nanobacteria is not able to grow, or has never been found without green one,
Endosymbiotic relationship needs another organism eg parasites such as ritizia inhibit eukaryotes, or hydrothermal vents that have endosymbiotic collonizing inner part , and providing nutrients
Consortium or microbial community, association of 2 or more diff organ, and when they exist they form and it is benefital to both org
Basic characteristics of symbiotic relationships that occur between different organisms
Basic characterists of symbiotic relationships that occur between diff organisms
Symbiosis doesn’t only mean positive
Diagram shows what type of relationship a symbiotic relationship is, mutualism is benefical to both,
But if we are looking at amensalism one way relationship, not benefical to one partner involved
Mutualism
some __________ to both partners relationship with some degree of
obligation often partners cannot live separately
mutualist and host are dependent on each other
Mutualism – selected examples: sulfide based mutualisms
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.
Relationships that occur within hydrothermal vent communityOn surface of ocean and ocean sediments and water Hydrothermal vents spew out fluid which is anoxic and contains sulfide, because on inc pressureWater does not boilBcs water has lolwer temp close to freezing actual area of therma vent activity cools down and supports microbial life
H2S can be used as electron donor, and H2s can generate new biomass by donating electrons by mocriorgs as energy
We find oxygenated cold water (o2 solubility inc with colder temps) Sulfates and carbon dioxides in thise enviornemnts Mocroorgs use H2S as source of electrons and energy when we get to mesophillic zone, microorgs able to survivve at mediate temps, These microbial activities hightened by donor properties and energy source and avalibility of electron source like oxygen
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
Endosymbiotic relationships, Tube worms eukaryotic found at bottom of ocean near hydrophobic vents Chemolithotrophic use inorganic molecules, they use H2S these endosymbiotic use H2S as electron source and use Co2 to generate organic material
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.
Tube worms bacterial relationships Co2 as carbon source produce organic material that is translocated through mem to animal tissue And can be used as source of energyChemolithotrophic deneration in the absence of photosynthesis form new light in inhospitable conditions at the bottom of the ocean
Chemosynthesis and C compounds can be used by higher organisms, mutualistic relationship because there is a relationship between tube worm and microorg (d), animal tube worm concentrates O, Co2 and H2S ( bcs it contains hemoglobin that can concentrate CO2 and H2S from sea water) and provide it to the microorg two way relationship
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?
Similar to mutualism but not obligatory relationship both partners profit
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 benefit or only one,
OM = organicmaterial
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
Syntrophic relationship, photosynthetic chromatium generates sulfate, and generates organic matter using Co2 as carbon source Able to use sulfate generate in sulfate reduction
Not mutualistic relationship. Or obligate Partners are not dependent but activities carried out by organisms cann be used by partner
Found in roots of plants, azotobacter fixes plants, free living N fixing, benefitted by glucose produced by celulomonas which breaks down cellulose
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?
Commensalism one way relationship
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
An Example of Commensalism
nitrificationNH3NO2 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.
End product is benefical for other organisms
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
Review questions – pg. 724
How does commensalism differ from cooperation?
Why is nitrification a good example of commensalism?
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
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
Attack gram neg microorgs
Grows inside microorg but inside plasma mem, grows and causes damage to cell a
Parasitism
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
Balance between parasite and host
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 not damaging completely until equi is disrupted by changes in lifestlye of host, and the host spreads infection to diff host in epidemic
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 controlled parasitism Demonstrated in lichens
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 on tree trunks, buildings and monuments
Fungus parisites host
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
Symbiant that lives inside host, over the years as parasite coinvolve, parasite reduces size of genome and it is veiwed as loss of genes because parasite doesn’t need metabolic paths to make own intermediates because its provided by host, host provides ATP or N in form of ammonia, bcs parasite doesn’t need to make it it looses genes to make this intermediate and therefore genome is smaller,
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 anitibiotics by fungi or bacteria, antibiotics inhibi other microorgs so that the strain gains an advantage over non antibiotic producing strain
Ex streptomycins, by ants
Competition
occurs when two organisms try to acquire or use the same resource
Nutrients electron donors, acceptors etc
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 sloww growing bact faster would outcompete slow moving bact, reduce numbersm resources limited, one microorg not able to outcompete one microorg numbers of both micrro would be reduced
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
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….
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
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 of more microbials cells or human cells,
1014 Interactions between humans and microflora these interactions complex and influence health conditions of host,
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)
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
Type of microorgs in human colon and why people are obese Publication showed that humans that had more firmicutes – grm post They had greater tendency to be obese, because firnmicutes extract energy from what people injest Could be due to food though
Human-Microbe Interactions
pathogenicity ability to produce pathological change
or disease pathogen
any disease-producing microorganismTolerating 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
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)
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
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
Diff types of symbiotic relationships Parasitic in some cases
Normal microbiota in various body sites: microorganisms typically encountered in various body sites.
She didn’t go through it,, or so she said
Anything exposed to outside, eyes ears mouth nose, and intestinne( gets input from outside) No don’t memorize all names of microorgs but don’t know all only couple coming up on slides to come
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)
Transient we pick up by touching surfaces, do not become established by may be associated with skin for some time,
Not ideal for mocroorgs because of shedding, and microorgs are lost from skin surface, and because of sweat skin also has lots of naCl, and harbours microorgs that can live in inc salt conc
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 components to unsaturated fatty acids and they are volitile which causes body odor too, causes in turn, acne
She wants us to remember this bacteria and know what genes it comes from Propionibacterium
Also used for cheese production ..
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
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 that removes microorgs Mucus contains macrophages which inhibity microbial microorgs
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)
Can be colonies by bact on moist Surface of eye
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
Mmany surfaces, surface of teeth junctions, gums and surface of tounge, soft pallet provides enviornemnt for growth of microorgs has many surfaces for attachment of microorgs
Research finds types of microorgs influence diabeties, types of microorgs and inflamatory responses and could effect diseases
http://www.britannica.com/EBchecked/media/68879/Anterior-view-of-the-oral-cavity
>700 species of bacteria
Hard surface of teeth
Soft tissue of oral mucosa
May microorbs have coating to help stick to surfaces,
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 microorgs are areobic
Anarobic niches (between teeth) formed and supports anaerobic growth for a healthy oral cavirty you need some of these to keep anaerobic bact in check, and its important to keep growth of all microorgs colonizing in check by brushing because microorgs use food remains in teeth as C sources and produce acidic end products
Caries (enamel damage due to acid formation)
Gingivitis (gums) Periodontal
disease (gums, bone)
http://www.textbookofbacteriology.net/normalflora_5.html
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 pylorihttp://www.youtube.com/watch?
v=u244Hwu51Hw
Has pilli that protect and are coated in mucus and it inc pH, and pH os neutral in the stomach
Microorgs cnnot grow, they are inhibited by acidic content but some can survive as they pass through because they are able to be exposed to pH or they can be injested by food, if found in food, not exposed to acidic enviornemnt one example helicobacter, colinizes epithelial surface, near surface Ph dec bcs epithelial cells have mucus to neutrilize pH and this bact eats carbs and nutrients coponents of mucus and the bact is the cause of ulcers and is associated with stomach cancer
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 three pats have microorgs, bacteria, and yeasts,
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 theres no air there, faculatative anaerbes found here too There are now many microorgs known, and great diversity many diff species, at least 400 diiff and are present, these microorgs live in association with epithelial cells coated in mucus, they are nutrient filled, Can be attached to food particles and aid digestions of food particles Microorgs benefit host by breaking down nutrients microorgs synthesize nutrients and fatty acids that help bread down food, mutualistic realationship because they get protection, and sources of energy
Overgrowth of pathogens causes problems
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 means there is an infection
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” ?
Colonize surfacesin intestine and prevent invasion, some microorgs secrete vitamins and transported into blood stream, equi exists in healthy body, and microorgs are beneficial and don’t cause harm mutally beneficial
Opportunistic causes changes in normal microbiota,
Lead to healthy enviornment, when pathogens change growth and over growth can occur, people are still trying to find the answer to this question
Scientists use gnotobiotic animals reveal a correlation between establishment of a stable microbial flora and the indiction of immune cometency Might be a multiple choice question
But she said focus on review questions they might be s/a questions e.G streptococci of viridans group, normally present in the mouth when introduced into blood stream in large numbers endocarditis
don’t want too much because overgrowth of good microorgs because produce acidic end products there are various niches in human body,
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
Test your knowledge
A pathogen is any disease producing microorg
A species bacter associated with oil glands of skin
A. staphylococcusb. pityrosporumc.propionibacterium
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
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?
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
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?
Next: food microbiology – chapter 40