346 Annals New York Academy of Sciences 



solutions containing 4 per cent CUSO4 in an industrial plant (Starkey and 

 Waksman, 1943). These forms grow well when submerged in nutrient-enriched 

 sulfuric acid solutions at pH values between 0.4 and 7.0. Some growth occurs 

 at pH (2.5 normal H2SO4) even when solutions are saturated with CUSO4 . 

 No study was made of the permeability of the cells to copper and hydrogen 

 ions, but presumably there was little to no penetration. 



One alga is notable for its growth in acid solutions, a strain of Cyanidhim 

 caldarium originally isolated from a hot spring containing 0.1 N H2SO4 . Allen 

 (1959) has cultured this form in 1 n H2SO4 . No attempt was made to deter- 

 mine whether growth would still occur in more concentrated solutions or acid 

 solutions at elevated temperatures. 



At the upper end of the pH scale many microorganisms are known to grow 

 actively at a pH of 10, some at a pH of 11, and a few others possibly at still 

 higher pH values. Johnson (1923) reported that limiting growth of Penicillium 

 var labile occurred in the pH range of 10.1 to 11.1. Two other fungi, Fusarium 

 hullatum and F. oxysporum, were limited by pH values in the range of 9.2 to 

 11.2. Many alkaline lakes are known with pH values in the range of 9 to 11, 

 and these are by no means sterile. Jenkin (1936) found populations of 13 

 algae, 4 rotifers, and 2 copepods living in the alkaline lakes of Kenya. In lakes 

 Elementeita and Nakuru, in which the pH was commonly in the range of 10 to 

 11, large concentrations (10^ individuals per ml.) of the blue-green a\a.ga.Arthrop- 

 sira platensis were found (Jenkin, 1936). Still more extreme cases of growth 

 at high pH have been reported by Meek and Lipman (1922) for Nitrohacter and 

 Nitrosomonas. They state that these forms multiplied in solutions with initial 

 pH values of 13.0, although not when the initial pH was as high as 13.4. These 

 results, however, seem rather surpising because of the apparent lack of a toxicity 

 effect due to ammonium hydroxide which would be expected for these forms 

 under the culture conditions used. Other workers have failed to corroborate 

 the findings of Meek and Lipman for Nitrobader and Nitrosomonas. Kingsbury 

 (1954) has reported that the blue-green alga Plectonema nostocorum will grow 

 in solutions of Ludox (a DuPont 30 per cent SiOo solution) adjusted to an initial 

 pH of 13, however the growth in this case was apparently limited to the surface. 



Salinity 



The range of salt concentrations tolerated by microorganisms during growth 

 and reproduction is enormous. Kalinenko (1957) has shown that some hetero- 

 trophic bacteria will multiply in double distilled water. (The water in this 

 case contained only 70 /xg. of organic matter per liter.) On the upper side it is 

 known that the fungi Aspergillus oryzae and A. terricola will grow in 4.1 m 

 MgS04 , a concentration equivalent to about 500 g. of salt per liter of solution 

 (Johnson, 1923). HalophiUc bacteria in nature grow abundantly in salt 

 Hmans, saturated brines, and on animal hides dried with concentrated salt solu- 

 tions. Even the Dead Sea with its salinity of 280 to 320 per thousand and high 

 bromide concentration is not sterile. A small gram negative rod, a yeast-like 

 form, and a green filamentous form were all found to grow and reproduce in 

 Dead Sea water enriched with 1 per cent peptone (Wilkansky, 1936). Other 

 bacteria and algae were also present. Some of the bacteria failed to grow in 



