Heat X-Philes: Bacteria

This group includes not only “simple” bacterial thermophiles, with an optimal growth temperature of anywhere from 50°C to 80°C (OGT=65°C±15°C), or 122°F to 176°F (149°F±27°F), but also bacterial hyperthermophiles, who have an optimal growth temperature over 80°C (OGT≥80°C) or 176°F (OGT≥176°F).

Here organisms are listed first by the upper end of their temperature range, then by OGT, then by the lower end of their temperature range, and for any organisms for which these properties are unknown or the same, they will be listed in alphabetical order.

Bacteria marked with an asterisk (*) are endospore-forming polyextremotolerant organisms. Bacterial endospores tend to give the bacteria capable of producing them polyextremotolerance. Endospores are known for being able to survive extremely high doses of radiation, vacuum dessication, extreme heat and cold, lack of nutrients, and in some cases even the passage of hundreds of millions of years (for example, Bacillus strain 2-9-3 was revived by scientists from 250-million-year-old spores (Vreeland, 2000); for comparison, the first dinosaurs began appearing about 220 MYA — 30 million years later). Although these endospore-forming bacteria can survive a variety of harsh conditions, endospore-formation is not done for reproduction, as with fungal spore formation, but is instead a last-ditch effort to survive conditions the bacterium would not otherwise be able to, which means these critters aren’t true polyextremophiles, because they don’t (necessarily) actually grow better in extreme conditions, and in their endospore form don’t even grow at all.

Bacteria marked with an asterisk (*) are endospore-forming polyextremotolerant organisms. Bacterial endospores tend to give the bacteria capable of producing them polyextremotolerance. Endospores are known for being able to survive extremely high doses of radiation, vacuum dessication, extreme heat and cold, lack of nutrients, and in some cases even the passage of hundreds of millions of years (for example, Bacillus strain 2-9-3 was revived by scientists from 250-million-year-old spores (Vreeland, 2000); for comparison, the first dinosaurs began appearing about 220 MYA — 30 million years later). Although these endospore-forming bacteria can survive a variety of harsh conditions, endospore-formation is not done for reproduction, as with fungal spore formation, but is instead a last-ditch effort to survive conditions the bacterium would not otherwise be able to, which means these critters aren’t true polyextremophiles, because they don’t (necessarily) actually grow better in extreme conditions, and in their endospore form don’t even grow at all.