Chapter 30 w2013 for students


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Chapter 30 w2013 for students

  1. 1. Chapter 30Microbial Interactions
  2. 2. Sections covered (overview) 30.1 microbial interactions 30.2 human microbe interactions 30.3 normal microbiota of the humanbody
  3. 3. Chapter objectives After reading this chapter, the student should be able to: discuss the term symbiosis as it relates to microorganisms, andgive examples of the theme areas mentioned above bydescribing the various interactions of microorganisms withone another and with nonmicrobial members of ecosystems describe examples of symbiosis in microorganisms found inextreme environments describe gnotobiotic animals and their importance inunderstanding the roles of microorganisms in higher organisms describe the body sites where normal microbiota are foundand give examples of the microorganisms found there
  4. 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 havemore than one symbiont associated with it:consortium physical association of two or more different organisms,usually beneficial to all Two difectosymfound o On redand in tthe e smsubarin Grows ois examnanobahas nevone, Endosyanotherritizia inhydrothendosyand pro Consortassociawhen thbenefita
  5. 5. Basic characteristics ofsymbiotic relationshipsthat occur betweendifferent organisms Basic csymbiooccur borganis Symbiomean p Diagramrelationrelationbenefic But if wamensarelationone par
  6. 6. Mutualism some __________ to both partners relationship with some degree ofobligation often partners cannot live separately mutualist and host are dependent oneach other
  7. 7. Mutualism – selectedexamples: sulfide basedmutualisms
  8. 8. Sulfide-basedmutualisms:Hydrothermal Ventsand RelatedGeological ActivityVent fluids are anoxic and contain hydrogensulfide. They can reach a T of 350oC, but thewater does not boil. Surrounding water haslower T.hinityeanut fluidsssurecloseermadH2SdonneweleceneWewatecoldSulfin thMocsouenemesabletemThehighpropsouelec
  9. 9. Tube Worm-BacterialRelationships exist thousands of metersbelow ocean surface nearvents chemolithotrophic bacterialendosymbionts live withina specialized organ(trophosome) of host tubeworm c, fix CO2 with electronsprovided by H2SSymbiotic chemolithotrophic bacteria withinthe symbiont-containing region of the bodywall of a marine worm, visualized with FISHand fluorescent microscopy. Bar=10 µmcanseyS asec
  10. 10. Tube worm-bacterialrelationshipsRiftia 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 hemoglobinand oxidized by endosymbiont bacteria.’s blood containsunique hemoglobin whichcaptures hydrogen sulfideand oxygen from seawaterin the trophosome packedwith chemolithotrophsEndosymbionts fix CO2 (from bloodstream, hemoglobin anddecarboxylation of e.g. malate andsuccinate) using e’s from H2S.Some of the resulting C istransferred to the host.ce organichroughof energyn in theorm news at theChemoscan be umutualisthere isworm anworm co( bcs it cconcentwater)two way
  11. 11. Review questions – pg. 722 How could you test if an insect-microberelationship is mutualistic? What is the critical characteristic of amutualistic relationship? What is the role of Riftia hemoglobin in thetube worm – endosymbiont relationship? How is the Riftia endosymbiont similar tocyanobacteria and how is it different?
  12. 12. milar to mutualism but not obligatoryationship both partners profit
  13. 13. Cooperation along with commensalism is a positive, but notobligate form of symbiosis which may involvesyntrophic relationships (“together-nourishment”) benefits both organisms in relationship syntrophism growth of one organism depends on or is improved bygrowth factors, nutrients, or substrates provided byanother organism growing nearby; sometimes bothbenefitBoth partners can b
  14. 14. OM =organicmaterialSelected Examples ofCooperative SymbiosisChromatium oxidizes sulfideto sulfate and providesorganic matter and electronacceptor to DesulfovibrioAzotobacter uses glucoseprovided by Cellulomonasand in turn provides fixednitrogeninNot mutuaobligate Pdependenby organispartnerFound infixes plabenefittecelulomocellulose
  15. 15. Review questions – pg. 724 How does cooperation differ frommutualism What is syntrophism? Is physicalcontact required for this type of arelationship – why or why not?
  16. 16. m one way relationship
  17. 17. Commensalism one organism Benefits_and the other (host) isNot harmed Commensal (lat. “together” & “table”) organism that benefits Not directly dependant, can survive separatedfrom host often syntrophic, e.g. products producedimprove growth can also involve modification of environmentby one organism, making it more suited foranother organisme.g.: synthesis of acidic wasteproducts during fermentationstimulates proliferation of acid-tolerant microorganisms
  18. 18. An Example ofCommensalism nitrificationNH3→NO2 →NO3 carried out by two differentbacteriae.g., Nitrosomonas carries outfirst stepe.g., Nitrobacter carries outsecond step (i.e., it benefitsfrom its association withNitrosomonas)FISH-based identification of ammonia-(blue) and nitrite-(red) oxidizing bacteria.ical for
  19. 19. More Examples microbial succession during spoilage of milk fermentative bacteria produce acids that promotegrowth of acid tolerant species skin or surface microbes on plants or animals host plant or animal releases volatile, soluble, andparticulate organic compounds, which are used bycommensals
  20. 20. Review questions – pg. 724 How does commensalism differ fromcooperation? Why is nitrification a good example ofcommensalism?
  21. 21. Predation among microbes, predation involves apredator species that attacks, usuallykilling its preyDescribes relationship by one bacteria attacks and kills otherbacteria or prey, one directional relationship and negativeconcequences
  22. 22. Microbial Predators Bdellovibrio penetrates cell wall,grows outside plasma membrane Vampirococcus epibiotic mode ofattacking prey, degradativeenzymes Daptobacter penetrates prey thendirectly consumes the cytoplasmiccontentsgsut insidecauses
  23. 23. Parasitism one organism gains parasite) and the other Isharmsed (host) always some co-existence between host andparasite successful parasites have evolved to co-existin equilibrium with their hosts if balance upset, host or parasite may dieween parasite
  24. 24. Balance Between Host andParasite Example – Typhus Rickettsia typhi is causative agentharbored in fleas, lives on ratstransmitted to humans by flea bites is endemic within population until societalchanges, e.g., war or other disruptionsoccur, and then becomes epidemicExists in equlibrium ncompletely until equichanges in lifestlye ohost spreads infectioepidemic
  25. 25. Another Example lichens, an example of a controlled parasitism association only occurs when organisms arenutritionally deprived mycobiont fungal partnerprovides water, minerals, sheltered environmentand firm substratum for growthphycobiontalga or cyanobacteriumprovides organic carbon and oxygenAlgea and fungus contrparasitismDemonstrated in lichen
  26. 26. lichens – associations of ascomycetes (mycobiont) andphotosynthetic bacteria (phycobiont)•Question: why is thisNOT classified as amutualisticrelationship?“Controlled parasitism”:some phycobioticcyanobacteria and algae growmore quickly when culturedaloneLichensbuilding
  27. 27. Genomic Reduction outcome of long-term parasiticrelationship parasite loses unused genomicinformation and can survive only inassociation with the host Example? Obligate intracellularbacteria, e.g. Rickettsia –grow in vertebrateerythrocytes, macrophages,vascular endothelial cells,depend on host for ATPde host,siteuces sizewed as losssite doesn’to makeause itsprovidesmonia, bcso make it ithisore
  28. 28. Amensalism Negative impact of one organism on another basedon release of a specific compound some examples Antibiotic production by fungi and bacteria use of antibiotic-producing streptomycin by ants to controlfungal parasites production of antibacterial peptides by insects and mammalse.g., cecropins, defensins, and athelicidinsProduction of aor bacteria, anmicroorgs so than advantageproducing straEx streptomyc
  29. 29. Competition occurs when two organisms try toacquire or use the same resourceNutrients electronetc
  30. 30. Two Possible Outcomes ofCompetition one organism dominates competitive exclusion principletwo organisms overlap too much in theirresource use, and one population isexcluded(e.g. slower growers) two organisms share the resource both survive at lower population levelsFast vs slowould outcreduce nuone microone microwould be r
  31. 31. Review questions – pg. 726,728 What is the competitive exclusion principleand where is this principle demonstrated inthe natural world? How are predation and parasitism similarand different? Discuss the relationship within lichens
  32. 32. Test your knowledge Mutualism is A. mutualist depentand on host B recipricol benefit both partners C. partners will not survive separately inmany cases D. all of the above….
  33. 33. T YOUR KNOWLEDGE In commensalism A. host and commensal can beseparated and remain viable B. the commensal is metabolicallydependent on the host C. host provides some factor thatcommensal cannot get otherwise
  34. 34. Section 30.2: Human-MicrobeInteractions the human body is a diverseenvironment specific niches are present More microbial cells or human cells? ecological principles apply to the manyinteractions that occur between the hostand its normal microbial flora Microbial flora, microbiota, microbiomeBody consists oor human cells,1014Interactions betwmicroflora theseand influence hehost,
  35. 35. Human-Microbe Interactions Microbial flora, microbiota, microbiome microbiome All the genes of the host and themicrobiota  composite geneticbackground goal is to determine the impact thatmicrobial gene function has on humanhealth (our genes do not encode theproducts needed for all biological functionsof the human body)
  36. 36. Human-Microbe Interactionse.g. some human traits (obesity?) may be influenced by bacteria(Firmicutes vs. Bacteroidetes?)•greater gene activation for proteins that catabolize complexcarbohydrates  more energy•trigger genes that slow host metabolismcolon andans thatsto beextractst
  37. 37. Human-Microbe Interactions pathogenicity ability to produce pathological change ordisease pathogen any disease-producing microorganismTolerating a normal microbiota suggests that the host derives benefit (e.g. viamin Kproduced by fecal coliformsMicrobial niches are defined by cellular receptors, surface properties, secretedproducts, etc….Host defense prevent microbes from establishing a parasitic or pathogenicrelationship
  38. 38. 27.3: Normal Microbiota of theHuman Body normal microbiota Microbes regularly found at an anatomicalsite that contacts the external enviornemnt( brain, blood, muscles) Internal tissues are normally freee ofmicrobesLifelong symbiotic relationship begins at birth(colonization of newborn depends onenvironment – e.g. breast fed infants)
  39. 39. Reasons to Study NormalHuman Microbiota to gain insight into possible infections resulting frominjury ( if we know who is there) to understand causes and consequences ofovergrowth of microbes normally abesent from bodysite To increase awareness of role played by indegenousmicrobe in stimulating immune response
  40. 40. Interactions Between a Hostand Its Normal Flora interactions include a broadrange of symbioticinteractions including commensalism mutualism parasitism examples of both ecto- andendosymbiotic relationshipsare present in the hostes
  41. 41. Normalmicrobiota invarious bodysites:microorganismstypicallyencountered invarious bodysites., or so sheAnything expmouth nose,outside)No don’t memicroorgscoming up on
  42. 42. Skin – 2m2 commensal microbes include both resident (grow onskin) 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 oiland sweat glands (many different phyla + yeast)y bemeeatndn live
  43. 43. Acne Vulgaris caused in part by activities ofPropionibacterium acnes Lipids fluid secreted by oil glands, hormonalactivity provide a hospitable environment for P.acnesChange lipids to unsaturated fatty acids (volatile,odiferous, active against gram-negative bacteria) inflammatory responseChanges lipid compofatty acids and they acauses body odor toacneShe wants us to rbacteria and knowcomes from PropioAlso used for cheese
  44. 44. 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) maycontain low numbers of potentially pathogenicmicrobes e.g., Streptococcus pneumoniae, Neisseriameningitidis, and Haemophilus influenzae
  45. 45. Respiratory Tract Upper and lower respiratory tracts haveno normal microbiota microbes moved by: continuous stream of mucus generated byciliated epithelial cells phagocytic action of alveolar macrophages lysozyme in mucusBody generates mucusmicroorgsMucus contains macropmicrobial microorgs
  46. 46. Eye from birth throughout a human life,small numbers of bacterial commensalsare found on the conjunctiva of the eye the predominant bacterium isStaphylococcus epidermidis (also S.aureus, Haemophilus, S. pneumoniae)s by bact on moist
  47. 47. Mouth Favourable environmennt – water, nutrients, pH contains organisms that survive mechanical removalby adhering to gums and teeth contribute to formation of ____________, dental caries,gingivitis, and periodontal disease Those that cannot attach are removed by mechanicalflushing to the stomach Shedding of epithelial cells removes microorganismscessoftemnthassforyffect
  48. 48. >700species ofbacteria Hardsurface ofteeth Soft tissueof oralmucosae coating tos,
  49. 49.  Colonized soon after birth by Streptococcus, Neisseria, Actinomyces,Veillonella (lactate fermenter), Lactobacillus, yeasts (aerobes andobligate anaerobes) First teeth – anaerobes Porphyromonas, Prevotella (Bacteroidetes),Fusibacterium (Fusobacteria)Streptococcus parasanguis, S. mutans -enamelsurfacesS. salivarius –buccal (the side of a tooth that isadjacent to the inside of the cheek) and gingivalepithelium, salivaProduce a glycocalyx and adherence factors thatallow them to attach to surfacesThese microorAnarobic nicheformed and sugrowth for a heneed some ofanaerobic bactimportant to kemicroorgs colobrushing becaufood remains inand produce a
  50. 50.  Caries (enameldamage due to acidformation) Gingivitis (gums) Periodontal disease(gums, bone)
  51. 51. Stomach most microbes killed by acidic conditions (pH2-3) 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 and are coated inH, and pH os neutral inMicroorgthey arecontent bsurvive athroughable to bor they cfood, if foexposedenviornehelicobaepitheliasurface Pepitheliato neutrilbact eatsnutrientsmucus acause ofassociatcancer
  52. 52. Small Intestine divided into three areas duodenumcontains _few organisms (acidic juices, bile, pancreaticsecretions; gram positives, enterococci, lactobacilli,Candida) jejunumEnterococcus, yeasts, lactobacilli ileumflora present becoming similar to that in colonpH becomes more alkaline  enterobacteria, anaerobicgram negativesThre areas, all thrbacteria, and yea
  53. 53. Large Intestine (Colon) largest microbial population of body, over 400different species isolated from feces, 1012organisms/g Anaerobic gram negatives, gram positive rods,Candida, protozoa, uncultivated eliminated from body by peristalsis, desquamation, andmovement 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 thetaoitamocrioncolonizes exfoliates host cells, food particles andsloughed mucusAnaerobic because theranaerbes found here toThere are now many midiversity many diff specpresent, these microorgepithelial cells coated infilled,Can be attached to fooddigestions of food particMicroorgs benefit host bmicroorgs synthesize nuhelp bread down food, mbecause they get protecOvergrowth of pathogen
  54. 54. 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 tomenstrual cycle acid-tolerant lactobacilli predominate  pH 4.4.-4.6  inhibitory to other organismsIf they have that me
  55. 55. The Relationship BetweenNormal 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 ofabnormalities, in foreign locations or in compromized hosts diseases opportunistic pathogens members of normal microbiota that produce disease under certaincircumstances; pathogens are prevented from causing disease bycompetition by normal microbiota (e.g. low pH prevents colonization byyeast) compromised host debilitated host with lowered resistance to infection (due to diabetes,malnutrition, cancer, etc.)  e,g, bacteroides (large intestine)  inperitoneal cavity or pelvic tissues  bacteremia “Everything is everywhere: but the environment selects” ?CointeinvsectranstreheamicandmuOpchamicLeaenvpatandocctryidon’t want too much because overgrowthof good microorgs because produce acidic
  56. 56. Test your knowlegse Microorgs commonly associate withhuman body are called normal microbial flora or thenormal microbiota Microbiota describes microorgs that colonizebody, and the microbiome is the study ofgenes of the microbiota that makes up thehuman body use structural genes to obtaininfo abot taxonomic relationships
  57. 57. Test your knowledge A pathogen is any disease producingmicroorg A species bacter associated with oilglands of skin A. staphylococcusb. pityrosporumc.propionibacterium
  58. 58. Tyour knowledge When members of normal microbiota ofhuman body bcm pathogenic andproduce disease they are calledpathogens D. opportunistic Ex strep in the mouth, c. diff in the intestine
  59. 59. Review questions – pg. 730,733, 736 Why is the skin usually not a favorable microenvironment forcolonization by bacteria? How do microorganisms contribute to body odor? What are the most common microorgansism found in various bodysites? Why is the colon considered a large fermentation vessel? What physiological processes move the microbiota through thegastrointestinal tract? Explain how the principle of competitive exclusion is used by normalhost microbiota in preventing the establishment of pathogens What is the difference between an opportunistic microorganism and apathogen?
  60. 60.  Diff btwn oppertunistic pathogen and apathogen? Why is colon considered largefermentation vesselBcs anaerobic environment and they dofermentation in the absence of oxygen
  61. 61. Critical thinking reviewquestions Describe an experimental approach todetermine if a plant-associated microbe iscommensal or mutualistic? Why do some patients who take antibioticsfor acne develop yeast infections of themouth or genital-urinary tract?
  62. 62. Next: food microbiology –chapter 40