Short-Term Exposure to Thermophilic Temperatures Facilitates CO Uptake by Thermophiles Maintained under Predominantly Mesophilic Conditions

Abstract

Three phylogenetically and phenotypically distinct CO-oxidizing thermophiles (Alicyclobacillus macrosporangiidus CPP55 (Firmicutes), Meiothermus ruber PS4 (Deinococcus-Thermus) and Thermogemmatispora carboxidovorans PM5T (Chloroflexi)) and one CO-oxidizing mesophile (Paraburkholderia paradisi WAT (Betaproteobacteria)) isolated from volcanic soils were used to assess growth responses and CO uptake rates during incubations with constant temperatures (25 °C and 55 °C) and during multi-day incubations with a temperature regime that cycled between 20 °C and 55 °C on a diurnal basis (alternating mesophilic and thermophilic temperatures, AMTT). The results were used to test a conjecture that some thermophiles can survive in mesothermal habitats that experience occasional thermophilic temperatures. Meiothermus ruber PS4, which does not form spores, was able to grow and oxidize CO under all conditions, while the spore-forming Alicyclobacillus macrosporangiidus CPP55 grew and oxidized CO during the AMTT regime and at 55 °C, but was not active at 25 °C. Thermogemmatispora carboxidovorans PM5T, also a spore former, only grew at 55 °C but oxidized CO during AMTT and 55 °C incubations. In contrast, the non-sporing mesophile, Paraburkholderia paradisi WAT, was only able to grow and oxidize CO at 25 °C; growth and CO uptake ceased during the AMTT incubations after exposure to the initial round of thermophilic temperatures. Collectively, these results suggest that temporary, periodic exposure to permissive growth temperatures could help maintain populations of thermophiles in mesothermal habitats after deposition from the atmosphere or other sources.

Screening of Cellulolytic Bacteria from Various Ecosystems and Their Cellulases Production under Multi-Stress Conditions

“…The sampling carried out at the level of the thermal spring of Ouled Tebben allowed the isolation of only eight bacterial strains, five of which were cellulase positive, and the presence of a reduced bacterial population is explained by the high temperature of the thermal waters. These natural high-temperature environments will certainly influence the resident microbial flora; the microorganisms able to grow and survive in these environments where the temperature exceeds 50 • C are thermotolerant or thermophilic [20]. A similar study demonstrated that only 16% of the bacteria isolated from the hot springs of western Algeria have cellulases; this type of unexploited biotope could constitute a promising source of thermophilic enzymes of great industrial importance [21].…”