Spectroscopic study of green sulfur bacteria in stratified water bodies of the Kandalaksha Gulf of the White Sea
A.A. Zhiltsova1, A.V. Kharcheva1, E.D. Krasnova1, O.N. Lunina2, D.A. Voronov1,3, A.S. Savvichev2, O.M. Gorshkova1, S.V. Patsaeva1
1Lomonosov Moscow State University, GSP-1, Leninskie Gory, 1/2, Moscow, 119991, Russia
2Winogradsky Institute of Microbiology, Leninsky pr-t, 33, build. 2, 119071, Moscow, Russia
3Institute for Information Transmission Problems of the Russian Academy of Sciences, Russia, 127051, Moscow, Bol'shoi Karetnyi per., 19
Keywords: аноксигенные фототрофные бактерии, зеленые серобактерии, флуоресценция, поглощение, бактериохлорофилл, Белое море, anoxygenic phototrophic bacteria, green sulphur bacteria, fluorescence, absorption, bacteriochlorophyll, the White Sea
Abstract
The optical characteristics of water in the stratified lakes of the White Sea are of particular interest in connection with the observation of thin colored layers around chemocline resulting from massive development of anoxygenic phototrophic bacteria. While the chlorophyll optical properties are widely used in remote sensing, the spectral characteristics of bacteriochlorophylls (BChl) for natural microbial communities have been little studied. Spectral study of green sulfur bacteria of four water bodies of the Kandalaksha Gulf of the White Sea was carried out in the work. Absorption and fluorescence spectra were measured for water sampled in March 2017 from various depths and compared with spectra of monocultures isolated from the same reservoirs earlier. It was shown that the fluorescence of BChl in the living cells of green sulfur bacteria has two overlapping emission bands: in the region 740-770 nm (BChl d and e) and at 815 nm (BChl a). The wavelength of maximum of the first band depends on the ratio of the concentrations of green-colored and brown-colored forms of bacteria containing different types of BChl. The new method for determination of contributions of two types of bacteria is proposed, based on the deconvolution of fluorescence spectrum into three bands which parameters were determined from the spectra of monocultures. The BChl content at various water depths was estimated and the percentage ratio of different types of phototrophic bacteria was determined.
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