THE RATE OF CO(2) ASSIMILATION BY PURPLE BACTERIA AT VARIOUS WAVE LENGTHS OF LIGHT

Area of Science:

• Microbiology
• Biochemistry
• Photosynthesis research

Background:

• Photosynthetic bacteria utilize pigments for light absorption.
• Spirillum rubrum possesses distinct green and red pigments involved in its physiology.

Purpose of the Study:

• To characterize the absorption spectra of pigments in Spirillum rubrum.
• To determine the role of specific pigments in the photosynthetic mechanism.
• To identify the primary light-absorbing pigment for CO2 reduction.

Main Methods:

• Spectrophotometric analysis of pigments in vivo and in vitro.
• Determination of wavelength sensitivity of the photosynthetic apparatus.
• Correlation of pigment absorption with photochemical activity.

Main Results:

• Absorption maxima for the green pigment in vivo at 420, 590, and 880 nm.
• Absorption maxima for the red pigment in vivo at 490, 510, and 550 nm.
• Wavelength sensitivity curve shows maxima at 590 and approximately 900 nm.

Conclusions:

• The green pigment, bacteriochlorophyll, is the primary light absorber for photosynthesis.
• The red pigment does not appear to function as a light absorber in this process.
• Bacteriochlorophyll directly drives photochemical CO2 reduction in Spirillum rubrum.