Microaerophilic bacteria grow best at reduced oxygen
tension; high oxygen tension is toxic to them.
4. Hydrogen ion concentration It is a measure of acidity and alkalinity. PH<7 is acidic PH =7 is neutral PH>7 ia alkaline Neutrophilic bacteria grow best at near neutral PH value. Acidicophilic bacteria prefer to grow at low PH value (acidic medium). Alkalinophilic bacteria prefer to grow at high PH (alkaline medium). Most pathogenic bacteria grow best at PH of 6-8. • • value • •
5. Salinity Salt content of the medium affects bacterial growth. Halophilic bacteria grow best at high salt concentration.
. Moderate halophiles require 3% salt concentration. . Extreme halophiles require 15% salt concentration. Most bacteia can not tolerate high salt concentration. High salt concentration disrupts membrane transport systems and denatures proteins of bacteria but halophiles have adaptive mechanisms to tolerate high salt concentration.