Lecture 7 - Microbial Interactions PDF

Lecture 7 Microbial interactions Assoc. Prof. Rebecca Case SCELSE/SBS [email protected]  Direct interactions 2 organisms only ~ involving Direct impact of one individual on another when not mediated or transmitted through a third individu...

Lecture 7 Microbial interactions Assoc. Prof. Rebecca Case SCELSE/SBS [email protected]  Direct interactions 2 organisms only ~ involving Direct impact of one individual on another when not mediated or transmitted through a third individual. In other words, A (donor) has an effect on C (recipient) Direct effects are thought to be more important than indirect effects in most ecosystems  Direct interactions used to describe multiple interactis symbiosis is Interaction Species X Species Y Mutualism + + Commensalism + 0 Predation involves + photosynthetic - specifically a Herbivory organism + - - , usually plant a & animal Parasitism - persistant ols doesn't kill , thos of of cost as + host e but parasite - Amensalism 0 - wants to host alive I keep Competition - - interact Neutralism 0 0 - no Table: Classic categories of direct effects in ecological communities. The sign (+, - , 0) represents the net effect of one species on the other species, either positive, negative, or neutral. Mutualism  Mutualism some reciprocal benefit to both partners relationship with some degree of obligation – partners may need to live together mutualist and host can be dependent on each other /totally inter-dependent endosymbiotic microbe provides needed vitamins and amino acids insect host provides secure habitat and nutrients e.g., aphid-Buchnera aphidicola interaction Deep sea tube worms Coral-Zooxanthellae coral-zooxanthellae-holobiont L microalque that make : corals green & is photosyntheticG it makes 90 % of e organic fori coral bacteria ~ to capture pathogen (intracellular microalques  highly reduced they fueled by tremolithotrophs photosynthetic organism are deep no ocean , in hydrogen sulfide - how? have which uses chemical sources of energy , they in which isa of electrons. On rich plume coming out through earth's crust source tube worm-bacterial water is - - e- to acceptor fuel energy ? generat relationships do fixate making organic C from inorganic they also CO2 , rich e sulfite T gills are in oxidisers (cremolithotrophs) that are ( makinge organic from water staken ~ sea into month piece I in plume water tubeworm adacenttocapillae ~ animal all & are sulfite oxidisers (animal cells) (endosymbiotic) plume water runs through capillary ~ Co-operation  Cooperation meaning organisms ais a - however, e interact is beneficial along with commensalism is a positive, but not obligate, for both of them form of symbiosis which involves syntrophic relationships benefits both organisms in relationship differs from mutualism because cooperative relationship is not obligatory relationships between sulfide-oxidizing bacteria and a variety of animals usually environments in rich hydrogen sulfide in – bacterium used as food source – e.g., sponges  underground cares forI auts to keep I temp ~ constant Fungal farming by ants = fungus Leaf cutting ants cultivate fungus ants a maintain feed e on fungus back as food by putting leafs & & they but come in ~ fungus eat fungal garden e Ants process leaves into small pieces, feed to fungi create for ants competitors & keep oute homes major it (Leucoagaricus sp.) fungus betw Fungus garden is susceptible to invasion by virulent fungal strains (Escovopsis sp.) art specifically inoculates a particular fungus to eat & feeds it w gop called it likes belong to leaves , other fungus will compete streptomyces famous well but i aut antibiotic path for i leaves as for will physicallycut inrading fungus antibiotics on it out a inoculate streptomycesi its (antibiotic treatment on to kill i fungus e fungus to exclude its competitors) Currie. 1999. Nature 398:701  ant host bacterial symbiont chalkywhite in Streptomyces's have a 7 Invasion of virulent characteristic fungus prevented mycelium and by bacterially aerial spore produced antifungal structures which is why they were first thought to be The test strain (producer): fungus. Streptomyces from ant The reporter strain (inhibited): Fungal antagonist of fungal garden  Ant’s fungal garden Leaf cutter ants form a cooperative relationship with a fungus The fungus (P) in farmed in ‘fungal gardens’ for the ant to eat and the ant provides it with pieces of leaves (C) for the fungus to feed off The ant cleans the fungal garden of invading species (often other fungus) The cleaning behavior of the ants involves inoculating the fungal garden with bacteria These bacteria produce bioactive compounds (antibiotics) against competing fungus (farmed fungus resistant) Recently found symbiotic nitrogen fixing bacteria (N) in the mix (C:N:P) Commensalism  Commensalism one organism benefits and the other is neither harmed nor helped (neutral) A commensal is an organism that benefits Often involve modification of environment by one organism, making it more suited for another organism habitat formers , microbial succession (Lecture 5) surface microbes on plants or animals – host plant or animal releases volatile, soluble, and particulate organic compounds, which are used by commensals  Nitrification Syntrophic interaction are metabolic interactions has consumer to find where one organism consumes another's waste poker poles e not benefitting frm consumer Nitrification: NH 3 >NO 2 > N O 3 ( L e c t u r e 6 ) – carried out by two different bacteria e.g., Nitrosomonas and Nitrobacter & Kommensal) converts nitrite to nitrate N > NOs- take ammonium and convert it to nitrite NO but I e nitrobactor is nitrosomonas looking NH3 > - for nitrosomonas is not looking for nitrobacter another e.. q bacteria plants a I commensal Predation  Microbial Predators among microbes involves a predator species that attacks, usually killing its prey partial Bdellovibrio penetrates cell wall, grows outside plasma membrane Vampirococcus epibiotic mode of attacking prey pierces things - I cell & sucks out Daptobacter penetrates prey then directly consumes the cytoplasmic contents Myxococcus “wolf pack” – cells use gliding motility to creep, overtake their prey, and release degradative enzymes ofhow for into they have diff strategies in terms they go I host all to consume I cytoplasm Myxococcus predation balls yellow  micro-colony E coli ~. Myxococcus - - Myxococcus it attaches & causes ~ lysis of I all it swarms into E coli colony as if consumes I cell contents they E make coli fruiting is bodies when consumed entirely e - they can stick to for & travel we animal to nxt site for colonisat  predator-prey relationships 1010 there is tipping point as not enough to be prey eaten 109 Cell Number /mL 108 107 predator 106 0 4 8 12 18 20 24 28 32 36 42 45 48 52 56 60 72 96 Time /h first followed by predator populate prey populati rise , causing predator no.f no. predator overconsume prey a prey due to food scarcity Lokta-Volterra relationship  Parasitism one organism benefits (parasite) and the other is harmed (host), which is measured as reduced size and fecundity - of offsprind always some co-existence between host and parasite no to ability => ↓ reproduce successful parasites evolve to co-exist with host – if balance upset, host or parasite may die 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  Ammensalism negative impact of one organism on another based on release of a specific compound this interact hard to maintain is 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 & negative impactmicrobes mammals on e.g., cecropins, defensins, and athelicidins – production of organic acids during fermentation  Competition occurs when two organisms try to acquire or use the ~ habitat , food , reproductive partners & etc. same resource one organism dominates there will be one party that - better slightly – competitive exclusion principal is two organisms overlap too much in their resource use, and one population is excluded two organisms share the resource – both survive at lower population levels  Indirect interactions Direct impact of one individual on another when not mediated or transmitted through a third individual. In other words, A (donor) has an effect on C (recipient) Direct effects are thought to be more important than indirect effects in most ecosystems Indirect impacts can be defined as the impact of one organism or species on another that is mediated or transmitted by a third. In other words, A (donor) has an effect on B (transmitter), which then affects C (recipient). g. malaria e.  Indirect interactions Interaction chain - a donor species affect the abundance of a transmitter and has an effect on a recipient often food in webs ~ grows better e.g. bird predation - caterpillar - herbivory, eaten baby formula in lactic acid from Bifidobacterium, inhibit - acidify make lastic acid - I envi & growth of pathogen, lowers disease incidence in infants modifyingsurvival each of e other species Interaction modification - the donor species alters some other attribute of the transmitter, such as behavior give through won't be interacti chain Soil isolate Streptomycetes antibiotic producer  as compound more made Soil isolate soil bacterium more cmpds made by cetes streptomy bar I - bacteria next e growing makes to it sigual/molecules is Streptomycetes tellingI streptomycetes that here a it will defend itself are stressed out they & don't have enough are unfrients ba : they how do we get it to polie making spores e antibiotics ? Indirect interactions ~ caterpillar plant/ bird , , myxococcus phototrophs/ & , heterotrophic bacteria in success  cascade Tropic top trophic level + if birds die , caterpillars t , plants if birds >> caterpillars , plants modifying [top-predators , alter survival you shift of I plant heterotroph autotroph  Myxococcus can eat can consume bacteria like autotrophs as heterotrophic E Coli. well Prochlorococcus ~ cneitheroccupy of these niches E. coli feeds on other microbial end pots Myxococcus Keystone Species  Keystone species humans e q. ~. Dominant species are species whose influence on their community is due to their high relative abundance Foundation species influence their community by facilitate & success physically changing their environment acidificate associate e.. g on habitat of light penetrate , I aut Keystone species are a species whose influence on its ecosystem and community is disproportional to its abundance g wolfs e.. indirect Tend to be high in the food web as their influence is often through trophic interactions (who is feeding on who) Keystone to community structure as they maintain it’s integrity and persistence through time diversity as well  lowest abundance , ~ top predator bottom trophic level species species of keystore species (top predators => lowers diversity "The species composition and physical appearance were greatly modified by the activities of a single native species high in the food web. These individual populations are the keystone of the community's structure, and the integrity of the community and its unaltered persistence through time." Paine (1969) large infestives : but taking in glycan rich food particle anaerobic system - microbes colonise it sheddinga, tells stick o s as slowgrowingorganism , ~ this retains bacterides as loss in system of them is associated & w disease states more  Bioactives Biologically active small molecules: signals, antibiotics and hormones Small molecule based interactions Defensive compounds, e.g. antibiotics, hydrogen peroxide etc. specific biological funct that cell ~ are to e not essential Secondary metabolites and central metabolism intermediates blocks to make needed for building an etc. TCA cycle fluff , things Dedicated signaling compounds is inhibited there is trong evolutionary growth a when , resistance to that pressure to acquire  Interkingdom interactions not zore inhibity , same microbe growing just white be it is not making anti-protozoa cmpd : not expressed which is purple= virulence features antibiotic poled by streptomycetes inhibiting fungus but continues to survive atea it isregulmakes seared a molecule that jams signaling system purple bacteria that inhibits diff protozoa cells  signaling that regulates a lot of virulence features ~ Quorum sensing - regulation in response to cell density Quorum sensing (QS) ubiquitous among microbes Density dependent chemical communication between bacteria that leads to rapid induction of phenotypes Coordinates gene expression at the population level First found in Gram + bacteria Streptomyces – prolific producers of cell-cell signals and bioactive compounds associated colonising hos/persistance host in I in ~ Often regulates phenotypes which modulate: o association with higher organisms or surfaces o virulence and symbisis " "want things to do as a group Synthesized inside cell and diffuses out only want to make e g.. a molecule if in e populate is making : signal molecules have to get outside of everyone molecule betw cells I all so it can signal common signaling systems System Distribution Phenotypes Widespread in Peptides competence and G+ sporulation, antimicrobial peptide production bioluminescence, virulence, AHL (AI-1) Proteobacteria biofilm formation, antimicrobial compounds, siderophores Widespread in AI-2 bioluminescence, virulence, G+ and G- biofilm formation γ-butyrolactone Streptomyces fruiting body formation and sporulation A, B, C, D Myxobacteria fruiting body formation and signals sporulation PQS Pseudomonas siderophore  AHL Quorum sensing system complex binds to Regulatory genes Structural genes that are quorum sensing regulated , recruitq &N pol, I R induce transcript : - & they can also shut down transcript by illuminescent response regulator shutte gere blocking par pol birding site , down genes Colonization Phenotypes forming a complex (e.g., swarming, biofilm formation, antimicrobials, virulence factors) synthase I R birdse signal AHLs produced Environment diffuse ind out of ecl)  AHL mediated quorum sensing Quorum sensing – ability to chemically sense cell density through signal concentration, where the signal concentration is a proxy for cell density Autoinduction (AI) is the self regulation of genes where a signal production is regulated by the signal itself (auto) First discovered in “bioluminescent” bacteria Cells glow due to production of luciferase enzyme (lux operon) luxI encodes AHL synthase luxR (response regulator) binds AHL (inducer) and positively regulates expression of lux (production of luminescence) genes What would be the benefit of one bacteria luminescing? Coordinate group behavior is the phenotype selected for in QS Rhizobium – symbiotic N fixing bacteria in root nodules with Rhizobium , symbiontnoduled must be able to infectI root it needs quorum sensing & to form e not module it also needs quorum etc sensing &. more Agrobacterium tumerfaciens – plant parasite plant is still growf , it has all e virulence genes on a plasma trsf through I popu that will only when it isa high density  Vibrio fischeri luminescent Epithelial cells & night they pump symbiosome , , i organ full of Or , Inmirescent & natients for bacteria them growth , it becomes a light organ , helps camouflage all e illuminescent i in morning if empties almost symbiosome d aif stopsallsupplying , basteria inside e & & urtrients bet they are low density Vibrio fischeri there , tell-to tell doesn't develop until basteria is organ squid for it to have a signaling betobacteria to milky seas illuminescent basters a -  sented inhibits i quorum sensing for purple pigmentat : O R O N H H O Acylated homoserine lactones R3 R2 Br O R4 O similar to seared makes - structurally homoserive Incore Halogenated furanones from Delisea pulchra they inhibit quorum sensing  Cross-talk Regulatory genes Structural genes I R Colonization Phenotypes (e.g., swarming, biofilm formation, antimicrobials, virulence factors) misfolds as furamores outcompete I binding I protein R 7 ACL for binding to ↑ all recycles I furamore -p complex & degrades it response regulator => shut down QS Furanones AHLs enter cell & Environment bind to response regulator & they have affinity more for binding  Furanones prevent AHL-mediated infection and bleaching by epiphytic bacteria Bleaching observed in late summer when ocean temperatures reach 24ºC Bleaching occurs at the mid- thallus where furanone concentration is lower Bleaching has been found to be temperature regulated in Vibrio shiloi infection of the coral Oculina patagonica  Colonisation and infection of furanone free D. pulchra by R11 - Furanones + Furanones 20ºC 25ºC 20ºC 25ºC Inoculate with Rugeria R11 & had QS barteria isolated from seared that  normal structa no basterial - colonist I surface even being inoculated - Furanones + Furanones it though is wi it micro-colonies of bacteria e on surface 20ºC Colonisation 25ºC Invasion and bleaching micro-colony gets through e epidermis & into e lower level & thats how it infects a causes I bleaching disease to spread  Bacterial Communication to host big advantage Not always species-specific (cross-talk) that can communicat corrupt as e e do ~ big advantage comm = infects & Some “eavesdropping” - them bad things Sensing what else is out there to establish survival strategy Co-ordinate group behavior - us More “us” than “them”? Potential targets for new antimicrobial drugs  Past exam questions 1) Which is an example of an indirect interaction? A.Keystone predation B.Metabolic symbiosis C.Parasitism D.Grazing E.r/K selection (not tested)  Past exam questions Complete the following table that lists an interaction (left column) between organisms A (a micro-organism) (middle column) and organism B (a maco-or micro-organism) (right column). None of the terms or organisms are repeated. interaction Organism A Organism B Competition Pseudomonas sp. Burkholderia sp. - - Amensalism Antibiotic producing bacteria Fungal parasite 0 - Commensalism Nitrosomonas (or ammonium Nitrobacter (or NO2 oxidiser) oxidiser) 0 + Mutualism Sulphide oxidating bacteria Tube worm + + Parasitism Agrobacterium tumefaciens plant + - Predation Myxobacteria Escherichia coli + -