Respuesta :
The chemotaxis medium we utilized provided sustained, exceptional motility. In it, temperature between 28°C and 42°C and pH between 5.5 and 9 had no effect on chemotaxis as assessed by capillary tests. With thresholds ranging from 3 nM for alanine to 0.1 mM for glutamate in the capillary assay and from 0.1 uM for alanine to 0.32 mM for glutamate in the microscope test, chemotaxis was seen toward all 20 common amino acids.
Chemotaxis toward amino acids in Bacillus subtilis.
- Bacteria move to higher concentrations of attractant or lower amounts of repellant through a mechanism called chemotaxis. Peritrichously flagellated bacteria such as Salmonella typhimurium, Escherichia coli, and Bacillus subtilis alternately swim and tumble in isotropic media (thrash about without making much forward progress).
- Bacteria migrate in the right direction by moderating tumbling frequency and, consequently, the distance swum in comparison to down slopes .
- Understanding what governs tumbling frequency and how this governing parameter is regulated by information from the receptors that bind the attractant or repellant are the key challenges in understanding how chemotaxis functions.
- According to Ordal, the Mg2+ ion interacts with the switch that regulates swimming and tossing, which determines the frequency of tossing. It is unknown how this Mg2+ ion concentration is controlled, though.
- Ordal has postulated that a methylated protein is engaged in this control based on the discovery that methylation of a membrane protein is intricately involved in chemotaxis .
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