y. 



Vallentyne: Environmental Biophysics & Microbial Ubiquity 343 



because of their great environmental and physiological diversLty as compared 

 to the so-called "higher" forms of Hfe. ^~ "^ 



Temperature 



The temperatm-e range for growth and reproduction of different microor- 

 ganisms extends from —18° to 104° C. These Hmits exceed those defining the 

 stability field of pure water under one atmosphere of pressure, but they do not 

 exceed the stabihty field of water in the liquid state when it is impure and under 

 variable pressure. 



Let us first consider some cases of microbial activity at temperatures below 

 0° C. It is important in this connection to realize that ice does not form in sea 

 water with a salinity of iS per thousand until the temperature drops below 

 — 1.9° C, and also that 90 per cent of all sea water has a temperature less than 

 5° C. It is thus not surprising to find that many marine bacteria will grow at 

 subzero temperatures. Bedford (1933) was able to culture 65 of 71 marine 

 bacteria from the north Pacific at subzero temperatures, and ZoBell (1934) 

 independently showed the same for 76 out of 88 marine bacteria in his collec- 

 tion. Ten of the taxa cultured by Bedford (1933) were capable of growth and 

 reproduction in nutrient-enriched salt solutions at — 7.5°C. Twelve others 

 grew at — 5°C. Horowitz-Wlassowa and Grinberg (1933) found 5 bacteria 

 that would grow at —5° C, and 14 others that grew at —3° C. Bacteria are 

 known to multiply in ice cream stored at —10° C. (Weinzirl and Gerdeman, 

 1929) and on fish stored at -11° C. (Redfort, 1932). 



Fungi, and probably algae as well, also multiply at these low temperatures. 

 Thus, the mold Sporotrichum carnis grows at —7.5° C. and very slowly even 

 at —10° C. (Haines, 1931). ChoelosLylum fresenii and Horniodendrou cladospo- 

 roides also grow at — 10°C. (Bidault, 1921). Tchistiakov and Botcharova 

 (1938) similarly found several different fungi that were capable of growth at 



— 8° C., although none of these would grow at —12° C. The flagellate Pyra- 

 mimonas (Pyramidomonas?) has been observed swimming in saline water at 



— 7.7°C. under the cover of ice in Lake Balpash, Kazakh S.S.R. (Zernow, 

 1944). Populations of 12 other photosynthetic forms were found in the same 

 water, presumably also alive and metabolizing. Zernow (1944) even observed 

 swimming Pyramidomonas and Dunaliella in drops of Lake Balpash water de- 

 rived from soft ice that had formed at —15° C. 



The most extreme cases of growth at low temperatures are those referred to 

 by Borgstrom (1961) who states that some molds and pseudomonads will grow 

 in concentrated fruit juices and sugar solutions at temperatures of — 18° to 



— 20°C. He has also observed the growth of Aspergillus glaucus kept in 

 glycerol at —18° C. A report of pink yeasts growing on oysters at tempera- 

 tures of —18° to —30° C. (McCormack, 1950) needs independent verification. 



No experiments seem to have been undertaken on the possibility of algal 

 photosynthesis in saline media at subzero temperatures, but such a result would 

 not be unexpected. Although slightly out of context, it is worth noting that 

 some terrestrial plants are able to carry out a limited photosynthesis at —2° 

 to — 3°C., and respire down to — 7°C. (Zeller, 1951). In the last century, 

 Jumelle (1891) reported that certain lichens and conifers could photosynthesize 

 at temperatures between —20° and —40° C., but modern studies have failed 



