Alkaliphiles grow optimally or very well at pH values above 9, often between 10 and 12, but cannot grow, or grow only slowly, at more neutral pH values. The enzymology, physiology, ecology, molecular biology and genetics of alkaliphiles, as well as industrial applications of these microorganisms have been investigated extensively and several enzymes have been put to use on an industrial scale.

Keywords: alkaline enzymes; sodium ions; pH; genetics

Figure 1.

The pH dependence of alkaliphilic microorganisms. Typical growth–pH dependence of neutrophilic and alkaliphilic bacteria are shown with squares and solid circles, respectively.

Figure 2.

Distribution of alkaliphilic microorganisms in environments of various pH.

Figure 3.

A schematic representation of cytoplasmic pH regulation.

Figure 4.

Circular structure of Bacillus halodurans C‐125 genome.



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Further Reading

Grant WD, Mwatha WE and Jones BE (1990) Alkaliphiles: ecology, diversity and applications. FEMS Microbiology Reviews 75: 255–270.

Horikoshi K (1999) Alkaliphiles. Tokyo: Kodansha.

Horikoshi K (2006) Alkaliphiles: Genetic Properties and Applications of Enzymes. Tokyo: Kodansha.

Horikoshi K and Akiba T (1982) Alkalophilic Microorganisms: A New Microbial World. Heidelberg: Springer.

Horikoshi K and Grant WD (eds) (1991) Superbugs. Heidelberg: Springer.

Horikoshi K and Grant WD (eds) (1998) Extremophiles: Microbial Life in Extreme Environments. New York: Wiley‐Liss.

Jones BE, Grant WD, Duckworth AW and Owenson GG (1998) Microbial diversity of soda lakes. Extremophiles 2: 191–200.

Kitada M and Horikoshi K (1980) Sodium‐ion stimulated amino acid uptake in membrane vesicles of alkalophilic Bacillus no. 8–1. Journal of Biochemistry 88: 1757–1764.

Kroll RG (1990) Alkaliphiles. In: Edwards C (ed.) Microbiology of Extreme Environments, pp. 55–92. New York: McGraw‐Hill.

Krulwich TA and Guffanti AA (1989) Alkalophilic bacteria. Annual Review of Microbiology 43: 435–463.

Krulwich T, Ito M, Gilmour R and Guffanti A (1997) Mechanisms of cytoplasmic pH regulation in alkaliphilic strains of Bacillus. Extremophiles 1: 163–169.

Krulwich T, Ito M, Hicks DR, Gilmour R and Guffanti A (1998) pH Homeostasis and ATP synthesis: studies of two processes that necessitate inward proton translocation in extremely alkaliphilic Bacillus species. Extremophiles 2: 217–222.

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Horikoshi, Koki(Jul 2008) Alkaliphiles. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1002/9780470015902.a0000337.pub2]