Thallium is highly toxic to humans and other mammals (ToxFAQs: Thallium)
and several radioactive thallium isotopes are known. In microorganisms, thallium is known to inhibit growth and to be accumulated
via potassium transport systems
(Norris et al, 1976; Damper et al, 1979).
Methylated thallium species have been detected in natural waters and production
of dimethylthallium by anaerobic microorganisms in lake sediment has been reported (Schedlbauer and Heumann, 2000.)
For more information:
Medline for thallium metabolism AND bacteria
Schedlbauer OF, Heumann KG. Biomethylation of thallium by bacteria and first determination of biogenic dimethylthallium in the
ocean. Appl Organometal Chem. 2000;14:330-40.