Dhakar Kusum, Pandey Anita
Biotechnological Applications, G. B. Pant Institute of Himalayan Environment and Development, Kosi-Katarmal, Almora, 263 643, Uttarakhand, India.
Appl Microbiol Biotechnol. 2016 Mar;100(6):2499-510. doi: 10.1007/s00253-016-7285-2. Epub 2016 Jan 16.
Microorganisms that inhabit the extreme pH environments are classified as acidophiles and alkaliphiles. A number of studies emerged from extreme high (hot springs, hydrothermal vents) as well as low temperature (arctic and antarctic regions, sea water, ice shelf, marine sediments, cold deserts, glaciers, temperate forests, and plantations) environments have highlighted the occurrence of microorganisms (thermophiles/psychrophiles) with the ability to tolerate wide pH range, from acidic to alkaline (1.5-14.0 in some cases), under laboratory conditions. However, the sampling source (soil/sediment) of these microorganisms showed the pH to be neutral or slightly acidic/alkaline. The aim of the present review is to discuss the phenomenon of wide pH range tolerance possessed by these microorganisms as a hidden character in perspective of their habitats, possible mechanisms, phylogeny, ecological and biotechnological relevance, and future perspectives. It is believed that the genome is a probable reservoir of the hidden variations. The extremophiles have the ability to adapt against the environmental change that is probably through the expression/regulation of the specific genes that were already present in the genome. The phenomenon is likely to have broad implications in biotechnology, including both environmental (such as bioremediation, biodegradation, and biocontrol), and industrial applications (as a source of novel extremozymes and many other useful bioactive compounds with wide pH range tolerance).
栖息在极端pH环境中的微生物被归类为嗜酸菌和嗜碱菌。一些来自极端高温（温泉、热液喷口）以及低温（北极和南极地区、海水、冰架、海洋沉积物、寒冷沙漠、冰川、温带森林和种植园）环境的研究强调，在实验室条件下，存在能够耐受从酸性到碱性的广泛pH范围（某些情况下为1.5 - 14.0）的微生物（嗜热菌/嗜冷菌）。然而，这些微生物的采样来源（土壤/沉积物）显示pH为中性或略呈酸性/碱性。本综述的目的是从这些微生物的栖息地、可能的机制、系统发育、生态和生物技术相关性以及未来前景的角度，讨论这些微生物所具有的广泛pH范围耐受性这一隐藏特性的现象。据信基因组是隐藏变异的一个可能储存库。极端微生物有能力适应环境变化，这可能是通过基因组中已存在的特定基因的表达/调控来实现的。这种现象可能在生物技术领域有广泛的应用，包括环境方面（如生物修复、生物降解和生物防治）以及工业应用（作为具有广泛pH范围耐受性的新型极端酶和许多其他有用生物活性化合物的来源）。
