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Class 11:Ecosystems:Governed by:Biotic componentsAbiotic componentsDistinguished by:ClimateVegetationStability/dynamic of ecosystem Dominate producerDominate consumerRichnessDiversity of speciesSimilar ecosystems have similar communitiesStratification important and controlled by temperatureProductivity affected by:How fast cells growNutrientsTurnover ratesCarbon availableFeeding strategiesLecture Study Guide:Know all the terms discussed in class today. Biosphere: total living world in all aspects of the environment.Ecology: study of the organisms and the biotic and abiotic elements of their environment.Ecosystem: abiotic environment and community that inhabits it Community: self contained group of interacting organisms that share the same habitat Populations: self contained interacting group of the same species Lithosphere: rocks, sediments, soils, weatheringHydrosphere: everything having to do with waterAtmosphere: what we and microbes can “breathe”; not just oxygenchemical/limiting factors: pH, nutrients (trace minerals), types of carbon available, lightBiomass: how much living material in an ecosystem, how much is producingBiogeochemical cycles: Decomposition: complex organic into simpler organic matter.Mineralization: breakdown of organic matter into inorganic.Assimilation: transformation or incorporation by organisms/microbes converting energy into nutrients.Immobilization: the incorporation of a simple, soluble substance into the body of an organism, making it unavailable for use by other organisms.What types of abiotic and biotic factors are important in controlling ecosystem processes?Abiotic: lithosphere, hydrosphere, atmosphere, chemical/limiting factorsBiotic: individual requirements/feeding strategies, biomass, production/productivity, decomposition, interactions (symbioses (definition: the living together or close association of two dissimilar organisms, each of these organisms being known as a symbiont), predator/prey, competition (definition: an interaction between two organisms attempting to use the same resources [nutrients, space, etc.]), population level, community level)What are the major differences between aquatic and terrestrial environments?Aquatic: ~stable C:N ratio. more constant C:N ratio because of the phytoplankton microbial loop within the aquatic systemsWinter: sunlight low, inorganic nutrients highSpring blooms→ high phytoplankton biomass Spring-Summer→ Inorganic nutrients are immobilized in phytoplankton cells, phytoplankton biomass dropsFall→ small bloom, inorganic nutrients increase in environmentTerrestrial: declining C:N ratio because of CO2 lost to the system and plant biomass. What controls primary production (the incorporation of CO2 into organic matter by photosynthetic organisms and chemosynthetic organisms)?Temperature, light, water, and nutrientsAquatic: temperature, light, nutrientsTerrestrial: temperature, water, nutrientsWhat is net primary productivity and how would one measure it?Rate after respiration, light-darkLight: gross productionDark: respirationDescribe the differences in primary productivity between terrestrial and aquatic environments?Aquatic: controlled by temperature, light and nutrients, can get nutrients and carbon from terrestrial run-off while terrestrial environments lose carbon primarily because plants incorporate carbon. (allochthonous)Terrestrial: controlled by temperature, water and nutrients, primary production from algae and cyanobacteria, terrestrial runoff, (autochthonous)What are the major microbes that perform primary productivity in biological soils?Cyanobacteria, algae, and lichensWhat is the difference between mineralization and immobilization?Mineralization: the conversion of organic nutrients into inorganic material during microbial growth and metabolismImmobilization: the incorporation of a simple, soluble substance into the body of an organism, making it unavailable for use by other organisms. inorganic→ organicWhat is decomposition controlled by? Net rate controlled by: C:N ratiosHow much energy is typically lost between trophic levels? Why?Approximately 90% (each trophic level only receives 10% of the energy found below it); 2nd law of thermodynamicsClass 12 Lecture Study Guide:What intrinsic properties of individuals influence population dynamics?Genetic composition- each individual has changes in genes that lead to physiological properties that affect ability to react.Physiological properties: stress tolerance, dormancy (endospores etc), plasticity (ability to adapt)What influences population structure? Be able to describe at least two factors in detail. Size: smaller cells = more surface areaDensity: over population, excess byproducts become toxicAge: old cells die- where in the growth cycle are cells, regulated vs unregulated growth. Distribution: geographic range/barriers, local populations, microniches (small groups, specialized in certain functions)What is microbial growth controlled by?-DIPDensity dependence: Stress Decreased reproductionQuorum sensingResource availabilityIntraspecific competition: competition within a populationInterspecific competition: between populations, within the same communityInteractions with different speciesPredation, disease, deathWhat are microbial growth rates controlled by?Resource typePhysiologyTemperature, pH, salt, growth strategies What are K- and r- strategies? Copiotrophs vs. oligotrophs? Why would one strategy be favored over another?K-selection:Grow slowOptimized to conserve environmental resourcesTypically resource-limited environmentsStable populationsExample: Comamonas acidovoransr-selection:High rates of reproduction (r = rapid)Populations subject to disturbancesGrow in erratic bursts, depending on inputOpportunisticDo not depend on othersExample: Aeromonas hydrophilar-selection is favored in copiotrophic environments (high concentrations of organic material) and K-selection is favored in oligotrophic environments (low concentrations of organic material)What factors influence individuals vs. populations?Individuals: genetic composition, physiological properties, adaptability (dormancy/persisters) Populations: structure, dynamics, and adaptations What is stochastic gene expression and what might happen with individuals within a population when this occurs? Def. = Random gene expressionCan produce signal that affects the rest of the population (e.g. exoenzymes, QS molecules, dormancy)What is the difference between dormancy and persisters? Dormancy: can be brought about by unfavorable conditions but it can also be random, no obvious change in morphology (maybe smaller because less RNA), not limited to endospores or cystsPersisters: during growth cells become dormant, don’t take in antibiotics because they aren’t reproducing How does QS influence population dynamics? 1. Production of signal molecule2. Release of it into environment3. Recognition of that molecule by other cells4. Changes in the gene regulationWhat are microbial cheaters? Is cheating a good strategy (for microbes, that is)?Take advantage of cells that are producingNot really the best method; good for mutated cells thoughClass 13 Lecture Study Guide:What is the definition and properties of a microbial community?Self-contained group of interacting organismsProperties: number of species, structure (relative abundance), turnover/turnover rate, functional redundancy, nichesWhat defines a niche? What are the properties of a niche?Populations/communities within a habitat, defined based on physiochemical environmental or interactions Can be functional (job) or physical (location)Properties: Patchy- clumps of bacteria interacting with each other in patches, structured by “what they’re seeing” physical and chemical environments or their interactions. What factors influence community structure?Interactions between species/functional nichesEnvironmental heterogeneity/physical nichesWhat is functional redundancy? How can you tell if there is a functional redundancy in a community?Functional redundancy- multiple taxa with overlapping functionsEach new taxa may have a function, but at some point this levels off. Stability of environment depends on functional redundancy- more diversity= more stability. They are capable of being stable in terms of functions they have in an environment. Redundancy makes it more likely to retain a function after stresses. Briefly describe some ecosystem services that communities provide.Conservation of matter: decomposition, organic to inorganic, inorganic to organic, nutrient cycling redox reactionsWhat defines a stable community? Succession? Stable community: Flexible compositions, temporal and spatial niches, temperature nichesSTABLE does not = STATICSuccession: colonization by primary/pioneer organisms, establishment of stable communityKnow the definitions of the terms in slide 16.Disturbance: event that causes change in a habitatPress: long-termPulse: short-termStability: when a community returns to its stable state after a disturbanceResistance: ability of a community to stay the same during and after a disturbanceSensitivity: how much a community changes during and after a disturbanceResilience: how fast a community recovers after a disturbanceWhat makes up a biofilm? Briefly outline the steps in biofilm formation.EPS (extracellular polymeric substance), CHO, proteins, glycoproteins, glycolipids, eDNA, e-enzymes1. Substratum preconditioning by ambient molecules2. Cell deposition3. Cell adsorption4. Desorption 5. Cell-to-cell signaling and onset of exopolymer production6. Convective and diffusive transport of O2 and nutrients7. Replication and growth8. Secretion of polysaccharide matrix9. Detachment, erosion, and sloughingWhat dictates the structure of a microbial mat? Why? How is a mat different than a biofilm? Similar? Light and chemicals dictates structure. They live at the interface of habitats or at the interface of biofilms Microbial mat is a type of biofilm that is found at interfaces of environments. Found in places such as surfaces of plants or floating on the ocean.List electron donors/acceptors and their products in order of energy generation. E- donor: CH2O → CO2, H2 → HF, CH3 → CO2, H2S → SO22-, ????????H2O → O2Class 14 Lecture Study Guide: What is alpha diversity?Number of species and relative abundance within a single communityWhat are the components to consider when studying the alpha diversity of a community?Number of species and relative abundanceSpecies evennessSimpson’s index (D)Measures the probability that two microbes chosen randomly from a community will be the same species-indicative of species evenness. When D is high (~1) the evenness is lowSimpson’s diversity index(1/D). Low ratio (closer to 1) = low diversityYou have a community with 50 individuals and 10 species.What type of distribution would you expect for an even community? What about an uneven community?Even: 5 individuals from each speciesUneven: every species has a different number of individualsWhat would you need to change in order for the community to become more rich?Add more species Each species has various functions What does a rank abundance curve show? What is plotted on each axis for these types of curves? Be able to interpret a plot.A species’ abundance compared to the other species in its communityX axis: rankY axis: abundance (percentage) Describe two common ways to illustrate beta diversity.DendrogramsOrdination plotsWhat is the difference between weighted and unweighted methods? Why would you use one method over the other?Weighted: accounts for abundance of each OTUUnweighted: + or -Similarity or dissimilarityMeasure between similar or diverse communities or over time/spaceWhat is Jaccard analysis? Bray-Curtis analysis?Jaccard: unweightedBray-Curtis: weightedWhat are the differences between Alpha and Beta Diversity?Alpha diversity is the measure of species richness of a communityBeta diversity is the rate of change in species composition from one community to another (turnover rate)Be able to interpret graphs, dendrograms, and ordination plots of diversity measures. Graphs: ranks the samples by their abundance in the community, a longer tail equals a more even communityDendrograms: nodes are sample names, determining the distance or similarity between the two samplesOrdination plots: closer the points are to each other, the closer the communities are to each other (similarities wise)Class 15 Lecture Study Guide:Know the difference between resistance and resilience. Describe what properties contributes to stability, resistance, and resilience at all levels (in individuals, populations, and communities). Be able to define those properties.Resistance is a community’s ability to stay the same during and after a disturbance, resilience is how fast a community recovers after the disturbanceIndividual- Stress tolerance, Plasticity (ability to change) and Going dormantPopulation- stochastic gene expression, Growth rate, adaptability and dispersal rateCommunity- Alpha diversity, turn-over rate, Microbial interactions, functional redundancy. Explain the difference between press and pulse disturbances. Which is more likely to change the community permanently? Why?Press is long-term and pulse is short-term; a press disturbance will more likely result in a permanent change because the long-term stress may permanently affect the condition of the environment and therefore affect the community that can exist thereClass 16 Lecture Study GuideExplain what symbiosis is in terms of microbial interactionsAssociation between two dissimilar organisms where both benefitDefinition given by Campbell- any persistent biological interaction that can be either obligate or facultative. What is the main difference between cooperation and mutualism?Mutualism is an obligatory relationship, cooperation is notWhat is syntrophy? Give a few microbial examples of mutualistic, cooperative, and commensal syntrophic interactions. Syntrophy: cross-feeding between two organismsMutualistic syntrophy: archaea-archaea: Nanoarchaeum equitans and Ignicoccus hospitalis (housing the larger N. equitans); Chlorochromatium aggregatum (once considered 1 organism) Inner cell is a rod shaped sulfur reducing bacterium. Comamonadacae will reduce sulfate to sulfide- will utilize acetate produced as a byproduct of photosynthetic bacteria such as Chlorobium. Chlorochromatium aggregatum will use sulfide as an electron donor. Cooperative syntrophy: methanogens: consumes hydrogen, making fermentation of propionic acid favorable; Desulfovibrio / Chromatium D- sulfate reducing bacteria, makes sulfide ?C- sulfur oxidizing. Takes sulfide and changes into sulfate. Sulfate is taken and used to grow, will produce CO2 and H2S that can be used by chromatium. Commensal syntrophy: two soil bacterial types, Bacillus cereus and population of Bacteroidetes; B. cereus makes peptidoglycan which promotes growth of CF rhizosphere bacteriaWhat are some general microbial examples of commensal interactions? All of these are considered environmental modifications (see below)Destroying toxinsChanging pH (acidic metabolic by-products)Removing oxygenWhat are the differences in the predatory mechanisms of the following:Myxococcus: secrete enzymes that lyses the prey, use up the organic matter from the lysed cells and change to fruiting body stage when all the organic matter is used up. 2 growth stages- one is vegetative and one is fruiting. It is a facultative predator. Bdellovibrio: grows in the periplasm and eventually kills the prey and lyses the cell, and goes back into the environment. Actively searches for prey; fast enough to swim and penetrate outer cell membrane- can kill gram negative bacteria. Why is coexistence or balance needed in parasitic interactions?Parasite must be in host for a minimum amount of time in order to reproduce and reach sufficient numbers to be able to colonize a new host. Ex. lysogenic virus. Ideal balance can result in long term relationship. Ex. lichens (only in book, she considers it mutualism). There must be a balance between killing the prey and surviving. ??What is amensalism? Why are bacteriocins an example? One organism negatively affects another due to production of a particular compound (eliminates competition)Bacteriocins: very specific antibiotics, target strains very similar to producer (producers have a specific protection mechanism), act by forming holes in plasma membraneName at least two interactions that free up resources and explain how this happens. Cheating- intraspecific or interspecific. Cheaters do not need to expend energy to make e-enzymes etc and can instead take in “public goods”. Can have high affinity or low affinity. Can have siderophores (iron affinity needed for microbes) or transporters. Cheaters can make a transporter and siderophores or can just have a transporter and take in iron that way. How is cheating related to competition with the siderophore example I talked about in class?See above- Can be normal and produce siderophores and transporters or can have a siderophore and a transporter with low affinity, this second type is not as competitive (Unsure of this slide)Class 17 Lecture Study GuideWhat types of locations can one find the microbes involved in plant-microbe interactions?Phyllosphere- above ground/aerial plant surface (stems and leaves)Rhizosphere- region around a plant root- not the surfaceRhizoplane- plant root surface. What is the phyllosphere? What type of microbial diversity would one expect to find there?- You would expect to find aerobic microbes. Exposed to rapid changes, UV light, humid environments, varied temperature. Contributes to global Carbon and Nitrogen cycling, and removal of pollutants (air, surface) and leaf decomposition Phyllosphere: aerial portion of plants(stems and leaves)Why are the rhizoplane and rhizosphere so rich in nutrients?Roots receive around 50% of the carbon produced by photosynthesis. Of this, 40 to 90% is put into the soil (plant exudates) (alcohols, sugars, amino acids, vitamins, nucleotides, etc.)What is the difference between Ectomycorrhizae and Endomycorrhizae?Endomycorrhizae- most common, penetrate the cell wall (arbuscular mycorrhizae is an example) Tropical plants or crops. Fungi gets carbs from plants, plants get stress protection and nutrients (drought protection, anti pest for nematodes) Ectomycorrhizae (more surface type) Mostly associated with trees in cooler environments. Transfer N and P to trees, Trees give carbohydrates. Mycelium grows around the root and thickens to form a sheath When Ectomycorrhizae are involved, how do nutrients get from the soil to the plant root cells?Hairs stem from the root into the soilWhat happens between plants and Rhizobia in nitrogen-rich soils? What about nitrogen-poor soils?Nitrogen-rich soils: plants secrete compounds that inhibit nodulationNitrogen-poor soils: inhibitory compounds are not produced, rhizobia can invade/infect the plantsNitrogenase is the most important enzymeExplain how root nodules for nitrogen-fixation form. What and how do Rhizobia contribute to form the nodules? How and what do the plants contribute?Conversion of N2 to NH3 by enzymes Symbiotic association between bacteria and plants-legumes1. Rhizobia are initially seen as invaders2. As a defense mechanism, the plants release an oxidative burst. ROS- general antimicrobial but rhizobia can defend itself. 3. Plant and rhizobia begin to exchange signals Plant produces flavonoids to stimulate the colonization of its rootsBacteria will attach to root hair cells4. Flavonoids bind to NodD (bacterial transcriptional regulator) and activate transcription of nod genes.5. Plant receives Nod factor signal Gene expression is altered in outer root cells- this re-initiates cell division to accept invading rhizobia6. Interaction thread formsNod factors and exopolysaccharides trigger changes in the plant plasma membrane7. Infection thread growsPasses through more plant cellsGrowth due to plant hormones and Nod factors8. Infection thread reaches the inner portions of the plants9. Bacterium is endocytosed by the plant cell into an unwalled membrane componentComponent + bacterium = symbiosome10. Within the symbiosome, bacteria differentiate into bacteroids- main function to fix nitrogen to ammonia- nitrogen factoriesTerminally differentiatedCan no longer divideEnlarge and alter morphology11. Many symbiosomes = root nodulePlants give amino acids, carbon and energy to bacteriaBacteria give nitrogen in amino acids to the plants Know what leghemoglobin is- nitrogenase enzymes are O2 sensitive, so leghemoglobin is produced by both plant and bacteria. It binds to O2 to sequester it. Plant makes one part and bacteria makes the other part to make a fully functional protein.***reminded me: need to know difference between doubling time and growth rate. doubling time is the time it takes for a population to double at a constant growth rate, dt= 70/growth rateDoubling time is the amount of time it takes for a given quantity to double in size or value at a constant growth rate. We can find the doubling time for a population undergoing exponential growth by using the Rule of 70. To do this, we divide 70 by the growth rate (r).Note: growth rate (r) must be entered as a whole number and not a decimal. For example 5% must be entered as 5 instead of 0.05. dt = 70/rFor example, a population with a 2% annual growth would have a doubling time of 35 years.35 = 70/2Thanks famClass 18 Lecture Study GuideWhy are the endosymbionts in the giant tubeworms found near deep sea hydrothermal vents chemolithoautotrophs? (What about the environment does or does not support the growth of particular types of microbes?)High concentrations of hydrogen sulfide, Mn2+, H2, and CO2Anoxic conditions, High temperatures, high pressure, no light Explain how the Riftia symbionts obtain their substrates for growth and energy production.Riftia Adults-no gut, juvenile- gut. Specialized hemoglobin carries H2S (e donor) and O2 and CO2 (carbon source)to symbiont. Trophosomes- are what used to be the gut, has a high cell density (~10^11 symbionts) What do the symbionts supply to their hosts? What do the hosts supply to the symbionts?Symbionts supply: O2, CO2, and reduced carbon compounds. Succinate and glutamate transferred to wormHosts supply: O2, CO2, H2S, NO3-, sulfideDo the Lucinidae (clams) symbionts supply all the carbon necessary for their host’s survival? ?How does this change with environmental change?Seagrasses are a good place for juvenile fish, crabs etc. When the grass dies- organic matter is produced. Sulfate reducing bacteria produce sulfide (from that organic matter). However, if there are clams present these bacteria would be in the gill cells - bacteriocytes. ?When housed in the gill the sulfide-oxidizing bacteria in Lucinidae (clams) give sugars to the bivalves, while the clams give the bacteria sulfide/oxygen. Less clams = higher rate of grass death because the sulfides produced by bacteria are toxic to the grassExplain the functions of the 4 major symbionts in the Olavius algarvensis symbiosis. 1. 2 sulfate reducers - anaerobic deltaproteobacteria 2. 2 sulfur oxidizers - aerobic ?dentrifying gammaproteobacteriaMost spirochetes are heterotrophs, they may have something to do with the detoxification of the worm. The advantage of having many is that they can be cycled through, hence sulfide and sulfate cycles occur directly within the worm. In addition, there is theory that there is a functional redundancy by having two of each type. They may also be able to metabolise different substances.What is common between most of these symbioses in terms of the benefit to the host? ?Compare these chemolithoautotrophc symbioses to the coral-zooxanthellae symbiosis.Symbioses of the three microbes listed above seems to provide metabolic pathways for the host. This is similar to that of the coral-zooxanthellae, that the algae provides materials for the coral polyps to grow and mature. Moreover, all four hosts provide safety and nutrient rich environment to prosper. However, the C-Z group uses photosynthesis, while the three listed are all chemolithoautotrophs ?Class 19 Lecture Study GuideWhat is/are the benefits for each member of the squid-Vibrio symbiosis?Squid benefits:Vibrio gives light to squid- can hide its shadow from predators Vibrio benefits:Safe and nutrient rich habitatHow are the bobtail squid colonized with Vibrio fischeri?Peptidoglycan triggers the squid to secrete mucus from the immature light organMucus causes gram-negative bacteria to aggregateIn aggregates, V. fischeri outcompete the other bacteria - form a “monoculture”V. fischeri is extremely motile and moves up ducts into the light organOnce in the light organ, V. fischeri becomes nonmotile (loses flagella)Establish dense populations and triggers development of light organ. NEEDS AUTO-INDUCER N-ACETYLHOMOSERINE LACTONE (recognize this at best)Once cell numbers reach a certain point, quorum sensing leads to light productionIn the morning, squid almost empties its light organ of bacteria, and bacteria regrowWhat selective pressures contribute to the specificity of this interaction between the squid and bacteria?Gram-negative selection by mucusNO (nitric oxide) gas- common defense by animal against pathogens, strong oxidant, present in the mucus/ light organs. V fischeri can tolerate What about this process is similar/different to the Legume-Rhizobia symbiosis?Similar: both use QS to communicate (p.153)Both use AHL’s to communicate with each other (Quorum-sensing)The bacteria is given a safe place to reside with a nutrient rich environmentThe plant receives nutrients and the organism gets a tactical advantageWhat general characteristics does the environment in the rumen have?pH between 5.5-6.5Protozoa also present but in smaller numbers, Total mass ends up being about the same for rumen and protozoa. If pH gets too acidic then protozoa die. Saliva buffers pHExplain the basic process of degradation of plant materials into VFAs by ruminants and their microbes. Microbes break down cellulose into glucose Glucose is fermented by bacteria into VFAs (acetate, propionate, butyrate) which the cows can use for energy. What changes in the microbial community occur when cows are fed a poor foliage diet, a grass diet, and a starch diet? Why?Poor foliage: fungi and high in complex plant material like cellulose and lignin (more Chytridiomycetes)Grass: High in cellulose (more Ruminococcus albus and Fibrobacter flavefaciens)High Grain diet-Starch (increases acidity of stomach). This can be a problem because the pH will be too low in the rumen. (more acid-resistant pathogens such as E. coli and Prevotella)What ruminant diet leads to an increase in human pathogens? Which human pathogens? Why? Grain Diet. This diet makes the environment more acidic and, since E. coli are resistant to acidosis, they become more prevalent in the cow’s gut and muscles. So, when people eat the meat from these cows, they often get food poisoning. Farmers often switch the cow’s diet from a grain diet to a grass diet before butchering in order to reduce the amount of E. coli in the stomach. THANK YOU whoever put this up <3 ?You’re very velcome :) 11 Notes: TermsBiosphere: total living world in all aspects of the environment Thin layer on earth, but microbes expand it. Ecology: study of the organisms and the biotic and abiotics of their environment Ecosystem: abiotic environment and the community that inhabits itCommunity: self contained group of interacting organisms, share the same habitatPopulation: self contained interacting group of the same species Biome: regional ecosystem (habitat)Ecosystems: Abiotic componentsLithosphere: rocks, sediments, soils, weatheringHydrosphere: everything having to do with waterAtmosphere: what we and microbes can “breathe”, not just O2Chemical/limiting factors: pH, nutrients (trace minerals), types of carbon available, lightBiotic groups:IndividualPopulationCommunityBiotic factors:Individual requirements/feeding strategiesBiomass: how much living material in ecosystemProduction/productivity: how much is producingDecompositionInteractionsSymbiosesPredator/preyCompetitionPopulation levelCommunity levelEcosystem ProcessesBiogeochemical cyclesC, N, P, SDecomposition: organic to organicHigher under anaerobic conditions Mineralization: organic matter into inorganic matterAssimilation: transformation or incorporate organisms/into microbes converting into nutrientsImmobilization: the incorporation of a simple soluble substance into the body of an organism, making it unavailable by use by other organismsKinds of Ecosystems:Governed by:Biotic componentsAbiotic componentsDistinguishing ecosystems:ClimateVegetationStabilityDominate producerDominate consumerRichnessDiversity of speciesMajor typesAquaticTerrestrialProduction/productivityFix energyPhotosynthesisChemosynthesisPrimary productivityGross: photosynthetic production of organic compounds (rate)Net: rate after respirationMeasured as kcal/m2/yr or gC/m2/yr? global productivity is by microbesPrimary Production in aquatic environmentsControlled by temperature, light and nutrientsStratification important and controlled by temperaturePrimary production in terrestrial systemsControlled by temperature, water and nutrientsPlants, algae, and cyanobacteriaDecomposition/mineralization and immobilization Terrestrial: C:N ratio decliningAquatic: C:N ratio are more constant because of the zitoplanktonBalance between processes?Energy conservationDifferences in where carbon/nutrients come from and end up between aquatic and terrestrial ecosystemsTerrestrial: autochthonous Aquatic: allochthonous, terrestrial runoffEnergy flow in EcosystemsKinds of energy: solar, chemical, mechanicalProductivityHow fast cells growNutrientsTurnover ratesCarbon availableFeeding strategiesClass 12 Notes:IndividualsGenetic compositionPhysiological propertiesStress toleranceDormancyPlasticity: ability to adaptAdaptabilityPhysiological heterogeneity: variation of individuals within a population“Developmental noise”Stochastic (random) gene expressiondormancy/persisters Quorum sensingMutantsCheatersHGT of antibiotic resistanceStochastic gene expressionSubpopulations most influentialCan produce signal that affects rest of populationExamples: exoenzymes, QS molecules, dormancyDormancy/PersistersCan be brought about by unfavorable conditions but it can also be randomNot limited to endospores or cystsNo obvious change in morphology, maybe smaller because less RNAPersisters: during growth cells become dormantSome 80-90% of cells in environment could be dormantQuorum SensingSteps:Production of signal moleculeRelease into environmentRecognition of that molecule by other cellsChanges in the gene regulationCheater CellsDon’t want to use energy, don’t have to produceStealing, randomAntibiotic resistanceExoenzymesQS moleculesIon-scavengingCan take advantage of the cells that are producingMicrobial PopulationsStructure, dynamics and adaptationsStructureSizeDensityAgeDistributionGeographic rangeLocal populationsMicronichesDynamicsextinction/bottlenecksDispersalTypes: geographic, physical, competition, predationFactors involved: nutrients, perspiration, escape from predators so they will disperse or sink ?GrowthRatesGrowth strategiesAdaptability within a population (individual) Population GrowthVBNC (viable but not culturable) genetic response to starvation Growth rate: K = n/tDoubling time: g = 1/kCarrying capacity: maximum sustainable population size, depends on the environment but in microbes because too many byproducts inhibit reactionsOverall Growth Controlled by?Density dependenceStressDecreased reproductionQuorum sensingResource availabilityIntraspecific competition: competition within a populationInterspecific competition: between populations, in the same communityPredation, disease, deathInteractions with different speciesGrowth RatesOther factors: temperature, pH, salt, growth strategiesHow active a cell migth beGrowth StrategiesR-selection High rates of reproduction (r)Populations subject to disturbancesGrow in erratic bursts, depending on inputOpportunisticDo not depend on othersCopiotrophsK-selectionGrow slowOptimized to conserve environmental resourcesTypically resource-limited environmentsStable populationsOligotrophsClass 13 Notes: ................
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