Chapter 30 w2013 for students

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