Chemotaxis

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  • 1. CHEMOTAXIS -Delince.J
  • 2. CHEMOTAXIS:  It is a phenomenon in which bacteria & other microbes moves towards or away from some chemicals present in the environment  This is very essential for microbes to search the food around them  There are two types of chemotaxis, 1. positive chemotaxis 2. Negative chemotaxis
  • 3.  POSITIVE CHEMOTAXIS: The movement of microbes towards a chemical is called positive chemotaxis.eg;food,nutrients  NEGATIVE CHEMOTAXIS: The movement of microbes away from the chemical is called negative chemotaxis.eg:toxins
  • 4. RHIZOSPHERE EFFECT  In 1904, Lorenz Hiltner coined the word rhizosphere.  Rhizosphere is the layer around the Root which is of 1-2mm thickness having Secretions ,  He described the rhizosphere effect in which he explained the predominance of microbial population in rhizosphere region
  • 5. HISTORY OF CHEMOTAXIS:  The migration of microbes is observed after the development of microscopy.  The first description is given by T.W.Engelmann(1881),W.F.Pfeffer(1884) in bacteria and H.S.Jennings in ciliates  Nobel laureate E.Metchnikoff also contributed in this research  At this time definitions for this phenomenon are also made
  • 6.  In 1970,1960’s revolution in microbiology created many techniques used to study this phenomenon .  On November 2006,Dr.Dennis Bray of Cambridge university got Microsoft European science award for his work on chemotaxis taking place in E.coli.
  • 7. Movement of phagocytes
  • 8. MOVEMENT OF BACTERIA
  • 9. CHEMOTAXIS IN SOIL  Many bacteria is growing near to the roots of some plants this is because of the exudates of roots in the rhizosphere region  So during plant growth the bacteria in the soil moved towards the roots exudates using the chemotactic activity to get nutrient  The root exudates contain vitamins , sugars, Organic acids , amino acids,etc which attracts the bacteria in the soil
  • 10. CONT’D  In rice fields, the chemotaxis cause movement of beneficial microbes towards the roots which are involving in nutrient cycle, protection to the plants etc.  They may create symbiotic relationship with the Plants  They may attract pathogens to the plant  For example isoflavin secreted by the root of Soya bean attracts a mutualist (Bradyrhizhobium japonicum)and also a pathogen(Phytopthora sojae).
  • 11. FACTORS AFFECTING CHEMOTAXIS  Chemical compounds present in the place affects the movement of microbes. For example, if the chemical is nutritive or useful to the bacteria it cause positive chemotaxis. If it is toxic or not useful to that then it cause negative chemotaxis  Temperature also affects this. For example p.florescence have good chemotactic activity at 30ºc
  • 12.  Other than these, chemotactic activity is affected by pH,water potential etc.  The water potential affects bacterial flow and the secretion of root exudates
  • 13. MICROBES ATTRACTED BY EXUDATES
  • 14. USE OF CHEMOTAXIS IN RHIZOBIUM  The plants of leguminaceae release a particular enzyme to attract the microbes .the rhizobium bacteria is attracted using chemotaxis and they produce signal of their arrival to the plant and cause the formation of root nodules
  • 15. THANK YOU