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SUMMARY:Dr Johannes Keegstra: Biophysics of aquatic microbes: randomness\, 
 energetics\, and sticky polysaccharides
DESCRIPTION:\n\n\n\n\n\n\n\n\n\n\n\n\n\n\nBiophysics of aquatic microbes: r
 andomness\, energetics\, and sticky polysaccharides \n\n\n\nAquatic ecosys
 tems are the world’s largest bioreactors\, but they are not well mixed a
 nd contain strong spatiotemporal heterogeneities\, giving rise to an envir
 onment where large outcomes are driven by small number of events\, and sto
 chastic effects are not averaged out despite the large scale. Specifically
 \, I describe recent work on bacteria searching for rich but dilute nutrie
 nt hotspots\, where we used microcalorimetry to quantify the cost of bacte
 rial motility\, that enhances bacterial encounters with such hotspots. Mot
 ility turns out to be the most expensive trait of a bacterial cell\, consu
 ming about 35% of total metabolism\, and gives rise to a risk-reward strat
 egy of motility endurance during energy limitation. Some bacterial species
  cease motility upon starvation to conserve resources\, others convert dai
 ly 10% of their biomass into energy to remain motile for days. Most cells
  will be unsuccessful in finding a hotspot but the few lucky ones keep th
 e population going. I also describe how sticky polysaccharides secreted by
  algae are potent chemoeffectors for bacteria to home in on such hotspots\
 , but only in close proximity of the algae. Further away\, bacteria need t
 o search for hotspots without clear navigational cues. However\, I show ho
 w the architecture of bacterial chemosensory arrays — large sensory pro
 tein complexes — exploits a phase transition to cause signalling fluctua
 tions that are useful in exploring such information deserts. Finally\, I a
 rgue that understanding these microscale interactions is paramount to a mo
 re predictive understanding of how microbes shape biogeochemistry and ulti
 mately our climate.\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\
 n\n\n\n\n\n\n\n\n
URL:https://www.imperial.ac.uk/events/214372/keegstra_microbes/
DTSTART;TZID=Europe/London:20261022T140000
DTEND;TZID=Europe/London:20261022T150000
LOCATION: SECB 326\, Sir Ernst Chain Building\, South Kensington Campus\, I
 mperial College London\, London\, SW7 2AZ\, United Kingdom
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