BIOSCI 206 – Principles of Ecology Lecture Notes

BIOSCI 206 University of Auckland BIOSCI 206 – Principles of Ecology Lecture Notes MICROBIAL ECOLOGY 1. All microbes are everywhere - Everything is everywhere, but the environment selects - Lourens Becking, inspired by Martinus Beijerinck - Botanist who pioneered work on microbial biogeography - Studied extremophiles in salt lakes and methane rich reservoirs - Organisms that thrived in high salt env turned up in that media Free-living microorganisms have the ability to get everywhere, but they only will thrive and survive if they are in an environment that suits them - Animals can’t disperse freely enough, resources limit them to environments - Microbes aren’t restricted in their distribution – travel around globe due to small size Factors for success – Small size of microbes allows passive dispersal >2mm - travel long distances - On global atmospheric currents - In 1987, storm transported 1.7-3m tons of dust from AUS to NZ Produces resting stages - spores - survive long distances - Resistant structures (spore) to survive desiccation, strong UV light - Structures within the cells allowing them to survive a very long time when needed - Blow somewhere and wait until conditions are suitable to rejuvenate and take over in those environments Asexual reproduction - Only need one cell in a new location to clone itself then take over in environment 2. Evidence - everything is everywhere Evidence - local surveys - Local habitats observed to contain most global diversity - Priests pot, UK - 20 microliters of sediment contained 40/50 known species of Paraphysomonas protozoa Biosci 206 BIOSCI 206 - distribute freely - they don’t get separated, don’t isolate – often find high diversity together/most of worlds diversity - Looked at all organisms present in lake – found with the smallest organisms, most can be found in single sample - <1mm probably are everywhere, larger start to get restricted Evidence - global surveys - Sampled different ocean surface waters around global - SAR11 bacteria found in most sites around world - In some areas, may represent 50% of total surface microbial community - Estimated to be 2.4x10^28 SAR11 cells in oceans – world’s most successful organism? - Huge biomass found everywhere - Highly abundant and distributed - Success may be aided by adapted strain divergence – populations not identical - 128 sites – differing temperatures – identified 9 main phylotypes/strains Evidence of passive dispersal on global currents - SAR11 found in ocean around world - Can look in atmosphere how well organisms being transported around - Sampled organisms in mid-low troposphere - 20% of particles in 0.25-1 micrometers were viable bacteria - Long distance transport – presence of marine bacteria in Hurricane earl samples taken far inland - Evidence of long distance transport - May mediate global climate as major cloud condensation nuclei 3. Active dispersal Passive dispersal – abiotic assistance - Transported around in atmosphere by global currents Self-propulsion – increase chances - P. keinii - shoot spores up to 2.5m using hydrostatic pressure - Fastest flights in nature compared to body size– launch speeds of 25m/s, acceleration of 180000g - Shooting spore onto new grass – new fresh energy source Protective mechanisms - survive transport and survive in new conditions - Thick spore structure around cell to prevent desiccation - Dark colours – high melanin to protect from UV light so DNA doesn’t degrade - Can slow down metabolism to 1% - Can dewater themselves into a husk to survive dry environments for long time period - Microbial spore e.g. – Bacilllus anthracis – resistant and resilient - Waterbears can also go through resting states – resilient and resistant Biosci 206 BIOSCI 206 Passive dispersal – biotic assistance - Move around on other organisms - Fungus infects insect and changes habit of insect to fly as high as it can before dying - Fly dies in high environment where fungus kills it – fugus erupts its spores high up on tree to be distributed more widely Animal dispersal - Red legged pademelon eats spores of at least 20 fungi along with many Australian mammals - Fungi produce good smell and taste to be eaten and distributed more widely by mammals - Spores can survive gut environment - In NZ, birds consume ground dwelling fungi and transport them around - Birds have less sense of smell and taste 4. Environment selects Microbial community response to physicochemical soil environment - Soil cores collected across great Britain - Observed distance-based gradient in community composition - Distance between any two samples collected - Found that further apart any two communities were collected, more different communities’ composition were - Related to env conditions Variability in community composition strongly linked to soil pH – env factor - High pH soils - more actinobacteria - Medium pH soil - more alphaproteobacterial - Low pH soils - group 1 acidobacteria dominates Predation – microbes’ response to biological soil env - Biocontrol fungus T. atroviride obliterates friendly AMF G. gigantea - Fungi vs fungi competition determines who survives in given environment Competition - No interaction - Competition – resources where neither does as well as on their own - Cooperation – work together to used shared resource - both do better than on their own Multispecies combinations of bacteria from pools in beech tree holes had decreased productivity (CO2 levels) vs monoculture - Competition or predation may be occurring Priority effects in fungi