Temperature Responses of Heterotrophic Bacteria in Co-culture With a Red Sea Synechococcus Strain

Abstract

Interactions between autotrophic and heterotrophic bacteria are fundamental for marine biogeochemical cycling. How global warming will affect the dynamics of these essential microbial players is not fully understood. The aims of this study were to identify the major groups of heterotrophic bacteria present in a Synechococcus culture originally isolated from the Red Sea and assess their joint responses to experimental warming within the metabolic ecology framework. A co-culture of Synechococcus sp. RS9907 and their associated heterotrophic bacteria, after determining their taxonomic affiliation by 16S rRNA gene sequencing, was acclimated and maintained in the lab at different temperatures (24–34°C). The abundance and cellular properties of Synechococcus and the three dominant heterotrophic bacterial groups (pertaining to the genera Paracoccus, Marinobacter, and Muricauda) were monitored by flow cytometry. The activation energy of Synechococcus, which grew at 0.94–1.38 d–1, was very similar (0.34 ± 0.02 eV) to the value hypothesized by the metabolic theory of ecology (MTE) for autotrophs (0.32 eV), while the values of the three heterotrophic bacteria ranged from 0.16 to 1.15 eV and were negatively correlated with their corresponding specific growth rates (2.38–24.4 d–1). The corresponding carrying capacities did not always follow the inverse relationship with temperature predicted by MTE, nor did we observe a consistent response of bacterial cell size and temperature. Our results show that the responses to future ocean warming of autotrophic and heterotrophic bacteria in microbial consortia might not be well described by theoretical universal rules.

Growth dynamics and transcriptional responses of a Red SeaProchlorococcus strain to varying temperatures

“…0.06 μm 3 for the two warmest experimental temperatures, although cell size increased systematically from 28°C to 30°C. A positive correlation between cell size and experimental temperature had also been noticed in a Synechococcus strain originally isolated from the Red Sea, as well as between environmental temperature and the cell size of a natural Synechococcus group in Red Sea shallow waters (Labban et al, 2021). We currently lack an explanation to this unexpected result, which nevertheless cannot be easily explained by diel changes in cell size (Palacio et al, 2020) since our pervasive relationship was based on simultaneous samplings of the five temperature cultures synchronized to the same light–dark cycle.…”

“…Cell abundance was measured using a BD FACSCanto II flow cytometer. The samples were stored, stained, and analysed following Labban et al (2021). The cytograms were analysed with the BD Paint-A-Gate software, which allowed us to clearly separate Prochlorococcus RSP50 cells from heterotrophic bacteria based on the red fluorescence (PerCP-Cy5-5, 498 nm) versus right angle light or side scatter (SSC) signals, as well as red versus orange fluorescence (PE, 433 nm) signals.…”

Microplastics Weaken the Adaptability of Cyanobacterium Synechococcus sp. to Ocean Warming

“…Similar growth rates and phenomena were observed in previous studies on the temperature response of Synechococcus sp. between 24 and 32 °C, , reflecting a laboratory plastic thermal adaptation of Synechococcus sp., even at extreme warming temperatures. Cells in the OW + MP treatments exhibited significantly ( p < 0.05) higher growth rates at 28 and 32 °C of 0.88 and 0.90 day –1 , respectively.…”

Interaction and Assembly of Bacterial Communities in High-Latitude Coral Habitat Associated Seawater

“…The co-culture system proved that the interaction between strictly heterotrophic bacteria and autotrophic strains played a crucial role in improving the CO 2 fixing efficiency by eliminating self-restraint of organic compounds and promoting the autotrophic pathway [ 13 ]. Moreover, such interaction was usually changed by temperature, seawater pH, and nutrient supplement [ 60 , 61 , 62 , 63 ]. Thus, the interactions between heterotrophic bacteria and carbon-fixers are essential for microbial community assembly.…”