Inter-Research
Aquatic Microbial Ecology

ABSTRACT: Spectroscopic analysis of nitrifying bacteria revealed the presence of a porphyrin-like pigment with an absorption maximum at 408 nm. The photoresponsive pigment accumulated during the late exponential phase of growth. The photoreceptor was found at higher concentrations in NH₄⁺ oxidizers than in NO₂^- oxidizers. When absorbance scans and action spectra of the nitrifiers were compared, it was found that the regression between the degree of photoinhibition and higher absorbances at 408 nm was significant (r² = 0.7). Reversible light-induced absorbance changes were observed in vivo and in vitro. Absorbance changes were maximally elicited by light in the 400 nm region for both types of nitrifiers, but the change was only significant (p < 0.05) for NH₄⁺ oxidizers. This spectral sensitivity of the NH₄⁺ oxidizing process suggests that the absorbance change observed is related to the blue light sensitivity of NH₄⁺ oxidizers.

KEY WORDS: Photoinhibition · Nitrifying bacteria · Nitrification

Published in AME Vol. 13, No. 3 (1997) on September 11
Print ISSN: 0948-3055; Online ISSN: 1616-1564. Copyright © Inter-Research, Oldendorf/Luhe, 1997