Influence of Oxygen on Tip Growth of Pilobolus Crystallinus Hyphae

ABSTRACT

Radial expansion of Pilobolus crystallinus colonies was inhibited by oxygen. The upper limit of pO₂ for radial growth was estimated at less than 30 mm Hg. At partial pressures of oxygen greater than 30 mm Hg the fungus only grew beneath the substrate surface and under an oxygen atmosphere (Po₂ = 760 mm Hg) growth ceased until respiration created an area of low pO₂ (<30 mm Hg) at the hyphal tips. Growth as measured by dry weight changes, however, was favored by aeration. Oxygen inhibits extension of hyphal tips which in turn effects vertical organization of the colony, but this fungus probably is not microaerophilic.

Key Words:

• Pilobolus
• tip growth
• oxygen
• aerotolerance