Communities of purple sulfur bacteria in a Baltic Sea coastal lagoon analyzed by pufLM gene libraries and the impact of temperature and NaCl concentration in experimental enrichment cultures

Abstract

Shallow coastal waters, where phototrophic purple sulfur bacteria (PSB) regularly form massive blooms, are subjected to massive diurnal and event-driven changes of physicochemical conditions including temperature and salinity. To analyze the ability of PSB to cope with these environmental factors and to compete in complex communities we have studied changes of the environmental community of PSB of a Baltic Sea lagoon under experimental enrichment conditions with controlled variation of temperature and NaCl concentration. For the first time, changes within a community of PSB were specifically analyzed using the photosynthetic reaction center genes pufL and M by RFLP and cloning experiments. The most abundant PSB phylotypes in the habitat were found along the NaCl gradient from freshwater conditions up to 7.5% NaCl. They were accompanied by smaller numbers of purple nonsulfur bacteria and aerobic anoxygenic phototrophic bacteria. Major components of the PSB community of the brackish lagoon were affiliated to PSB genera and species known as marine, halophilic or salt-tolerant, including species of M arichromatium, H alochromatium, T hiorhodococcus, A llochromatium, T hiocapsa, T hiorhodovibrio, and T hiohalocapsa. A dramatic shift occurred at elevated temperatures of 41 and 44°C when M arichromatium gracile became most prominent which was not detected at lower temperatures.

Distribution of Phototrophic Purple Nonsulfur Bacteria in Massive Blooms in Coastal and Wastewater Ditch Environments

“…In addition to these findings, the pufM gene amplicon analysis has clearly shown that the major phylotypes detected were those assigned to the genera Thiolamprovum and Thiocapsa in the pink mudflat and to Marichromatium and Thiocapsa in the red tide pools. Similar PSB members accompanied by smaller numbers of PNSB and aerobic anoxygenic phototrophic bacteria have been found in massive blooms in a brackish lagoon [8]. To our knowledge, therefore, the formation of red-pink blooms in coastal environments is attributable to massive development of PSB, and the contribution of PNSB as the colorants to the bloom formation is less significant.…”

“…The available information on the occurrence of PNSB in colored microbial mats and blooms in the environment has so far been only scattered and fragmentary [8,[19][20][21]. As reported herein, our polyphasic approach to address this issue by culture-independent techniques as well as by conventional cultivation methods has improved information on the distribution of PNSB in colored blooms/mats in terms of quantity and quality.…”

“…Sunlight-exposed stagnant water bodies in natural and engineered environments that contain sulfide and/or high-strength organic matter are rich sources of the phototrophic purple bacteria, which often exhibit massive growth, as seen as red, pink, and brown blooms and microbial mats. The massive development of the phototrophic purple bacteria can be seen in specific habitats [1], including meromictic lakes [2][3][4][5][6], lagoons in intertidal zones [7,8], salt marsh and lakes [9,10], shallow soda pans [11], and wastewater stabilization ponds [12][13][14][15][16][17][18]. Naturally occurring massive blooms are mainly caused by the proliferation of the purple sulfur bacteria (PSB), which comprise the family Chromatiaceae within the class Gammaproteobacteria.…”

“…Quinone profiling is a chemotaxonomic biomarker method useful for roughly determining microbial populations in terms of quantity and quality [22,23]. The clone library analysis of pufLM genes, encoding the L and M subunits of photochemical reaction center proteins, is useful to classify PSB and PNSB phylotypes in mixed populations for which 16S rRNA genes are not suitable as phylogenetic markers [8,10,19,[24][25][26]. We also determined the genome sequence of Rhodovulum sp.…”

New Dimensions in Microbial Ecology—Functional Genes in Studies to Unravel the Biodiversity and Role of Functional Microbial Groups in the Environment

“…Although this fraction of the more abundant organisms could be regarded to include the most important players (at least under the conditions and the time of sampling) by no means it represents the potential of a selected sample and habitat under variation of the environmental conditions. In fact, changes of the environmental conditions are expected to provoke significant and complex changes of the community composition with the effect that minor and not detected members of the community become major or even dominant parts of it [ 9 ]. Probably one of the most extreme realizations of this effect is seen in enrichment cultures used by generations of microbiologists to specifically manipulate the natural community.…”