Large‐scale distribution and activity patterns of an extremely low‐light‐adapted population of green sulfur bacteria in the Black Sea

Abstract

The Black Sea chemocline represents the largest extant habitat of anoxygenic phototrophic bacteria and harbours a monospecific population of Chlorobium phylotype BS-1. High-sensitivity measurements of underwater irradiance and sulfide revealed that the optical properties of the overlying water column were similar across the Black Sea basin, whereas the vertical profiles of sulfide varied strongly between sampling sites and caused a dome-shaped three-dimensional distribution of the green sulfur bacteria. In the centres of the western and eastern basins the population of BS-1 reached upward to depths of 80 and 95 m, respectively, but were detected only at 145 m depth close to the shelf. Using highly concentrated chemocline samples from the centres of the western and eastern basins, the cells were found to be capable of anoxygenic photosynthesis under in situ light conditions and exhibited a photosynthesis-irradiance curve similar to low-light-adapted laboratory cultures of Chlorobium BS-1. Application of a highly specific RT-qPCR method which targets the internal transcribed spacer (ITS) region of the rrn operon of BS-1 demonstrated that only cells at the central station are physiologically active in contrast to those at the Black Sea periphery. Based on the detection of ITS-DNA sequences in the flocculent surface layer of deep-sea sediments across the Black Sea, the population of BS-1 has occupied the major part of the basin for the last decade. The continued presence of intact but non-growing BS-1 cells at the periphery of the Black Sea indicates that the cells can survive long-distant transport and exhibit unusually low maintenance energy requirements. According to laboratory measurements, Chlorobium BS-1 has a maintenance energy requirement of approximately 1.6-4.9.10(-15) kJ cell(-1) day(-1) which is the lowest value determined for any bacterial culture so far. Chlorobium BS-1 thus is particularly well adapted to survival under the extreme low-light conditions of the Black Sea, and can be used as a laboratory model to elucidate general cellular mechanisms of long-term starvation survival. Because of its adaptation to extreme low-light marine environments, Chlorobium BS-1 also represents a suitable indicator for palaeoceanography studies of deep photic zone anoxia in ancient oceans.

The energetics of anabolism in natural settings

“…This scenario is shown with the dashed line in Figure 1. A basal maintenance power of 1.9 × 10 − 19 J s − 1 is used in conjunction with Equation (8) to generate this line, a value of P d that is two order of magnitude lower compared with the lowest reported maintenance energy in the literature (Marschall et al, 2010). An organism existing in this energy state would only use 6 × 10 − 9 J cell − 1 over the course of 1000 years, more than two orders of magnitude less energy than the aerobic heterotroph uses for ΔG main in 1 month.…”

Core Fluxome and Metafluxome of Lactic Acid Bacteria under Simulated Cocoa Pulp Fermentation Conditions

“…However, it remains unclear how individual strains succeed in such a complex ecosystem and how they specifically contribute to the overall metabolite profile of fermented cocoa pulp. Even if subpopulations are enumerated, the cell number of individual species cannot directly be correlated with their metabolic activity, because viable cells may be less metabolically inactive than others (15). In this regard, a straightforward approach for elucidating the metabolic interactions between individual species is 13 C-based metabolic flux analysis.…”

Identification and Targeted Cultivation of Abundant Novel Freshwater Sphingomonads and Analysis of Their Population Substructure

“…For the extraction of DNA and RNA, cells from 250 to 500 ml of lake water from Walchensee and Starnberger See lakes were collected onto Isopore polycarbonate membrane filters (pore size, 0.1 m; diameter, 47 mm; Millipore GmbH, Schwalbach, Germany). DNA was extracted using the protocol of Fuhrman et al (19) as modified by Marschall et al (35). Concentrations were determined by fluorescent dye binding with PicoGreen (Invitrogen, Karlsruhe, Germany) employing a microtiter plate reader (Tecan Infinite M200; Männedorf, Switzerland).…”