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alkaliphile
Alkaliphiles are a class of extremophilic microbes capable of survival in alkaline (pH roughly 8.5-11) environments, growing optimally around a pH of 10. These bacteria can be further categorized as obligate alkaliphiles (those that require high pH to survive), facultative alkaliphiles (those able to survive in high pH, but also grow under normal conditions) and haloalkaliphiles (those that require high salt content to survive).〔HORIKOSHI, KOKI. "Alkaliphiles: Some Applications of Their Products for Biotechnology." MICROBIOLOGY AND MOLECULAR BIOLOGY REVIEWS 63.4 (1999): 735-50. Print.〕
==Background information==
Microbial growth in alkaline conditions presents several complications to normal biochemical activity and reproduction, as high pH is detrimental to normal cellular processes. For example, alkalinity can lead to denaturation of DNA, instability of the plasma membrane and inactivation of cytosolic enzymes, as well as other unfavorable physiological changes.〔Higashibata, Akira, Taketomo Fujiwara, and Yoshihiro Fukumori. "Studies on the Respiratory System in Alkaliphilic Bacillus; a Proposed New Respiratory System." Extremophiles 2 (1998): 83-92. Print.〕 Thus, to adequately circumvent these obstacles, alkaliphiles must either possess specific cellular machinery that works best in the alkaline range, or they must have methods of acidifying the cytosol in relation to the extracellular environment. To determine which of the above possibilities an alkaliphile uses, experimentation has demonstrated that alkaliphilic enzymes possess relatively normal pH optimums. The determination that these enzymes function most efficiently near physiologically neutral pH ranges (about 7.5-8.5) was one of the primary steps in elucidating how alkaliphiles survive intensely basic environments. Because the cytosolic pH must remain nearly neutral, alkaliphiles must have one or more mechanisms of acidifying the cytosol when in the presence of a highly alkaline environment.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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