67:, as well as other unfavorable physiological changes. 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. Since the cytosolic pH must remain nearly neutral, alkaliphiles must have one or more mechanisms of acidifying the
47:
230:. It is hoped that further research into alkaliphilic enzymes will allow scientists to harvest alkaliphiles' enzymes for use in basic conditions. Research aimed at discovering alkaliphile-produced antibiotics showed some success, yet has been held at bay by the fact that some products produced at high pH are unstable and unusable at a physiological pH range.
182:– would be severely reduced. However, the opposite is true. It has been proposed that while the pH gradient has been reversed, the transmembrane electrical potential is greatly increased. This increase in charge causes the production of greater amounts of ATP by each translocated proton when driven through an ATPase. Research in this area is ongoing.
139:
counterpart. When alkaliphiles lose these acidic residues in the form of induced mutations, it has been shown that their ability to grow in alkaline conditions is severely hindered. However, it is generally agreed upon that passive methods of cytosolic acidification are not sufficient to maintain an
37:
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
160:
extrusion establishes a proton gradient that drives electrogenic antiporters—which drive intracellular Na out of the cell in exchange for a greater number of H ions, leading to the net accumulation of internal protons. This proton accumulation leads to a lowering of cytosolic pH. The expelled Na can
177:
In addition to the method of proton extrusion discussed above, it is believed that the general method of cellular respiration is different in obligate alkaliphiles as compared to neutrophiles. Generally, ATP production operates by establishing a proton gradient (greater H+ concentration outside the
338:
Hirabayashi, Toshikazu, Toshitaka Goto, Hajime
Morimoto, Kazuaki Yoshimune, Hidetoshi Matsuyama, and Isao Yumoto. "Relationship between Rates of Respiratory Proton Extrusion and ATP Synthesis in Obligately Alkaliphilic Bacillus Clarkii DSM 8720T." J Bioenerg Biomembr 44 (2012): 265-72.
178:
membrane) and a transmembrane electrical potential (with a positive charge outside the membrane). However, since alkaliphiles have a reversed pH gradient, it would seem that ATP production—which is based on a strong
161:
be used for solute symport, which are necessary for cellular processes. It has been noted that Na/H antiport is required for alkaliphilic growth, whereas either K/H antiporters or Na/H antiporters can be utilized by
54:
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
194:
and future research. Alkaliphilic methods of regulating pH and producing ATP are of interest in the scientific community. However, perhaps the greatest area of interest from alkaliphiles lies in their
320:
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.
329:
Krulwich, Terry A., Mashahiro Ito, Ray
Gilmour, and Arthur A. Guffanti. "Mechanisms of Cytoplasmic PH Regulation in Alkaliphilic Strains of Bacillus." Extremophiles 1 (1997): 163-69. Print.
140:
internal pH 2-2.3 levels below that of external pH; there must also be active forms of acidification. The most characterized method of active acidification is in the form of Na/H
169:
or another means, the bacteria are rendered neutrophilic. The sodium required for this antiport system is the reason some alkaliphiles can only grow in saline environments.
79:
Alkaliphiles maintain cytosolic acidification through both passive and active means. In passive acidification, it has been proposed that cell walls contain acidic
304:
Horikoshi, Koki. "Alkaliphiles: Some applications of their products for biotechnology." Microbiology and
Molecular Biology Reviews 63.4 (1999): 735-50. Print.
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362:
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56:
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469:
104:
100:
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46:
16:
Extremophile microbes capable of survival in alkaline (pH roughly 8.5 – 11) environments
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108:
50:
A typical bacillus culture. Many alkaliphiles possess a bacillus morphology.
569:
542:
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434:
166:
80:
30:
26:
103:. Together, these residues form an acidic matrix that helps protect the
605:
207:
195:
68:
64:
351:
Extremophiles: Sustainable
Resources and Biotechnological Implications
595:
149:
112:
45:
374:
378:
34:
316:
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310:
144:. In this model, H ions are first extruded through the
71:
when in the presence of a highly alkaline environment.
107:
from alkaline conditions by preventing the entry of
693:
643:
604:
541:
532:
412:
165:bacteria. If Na/H antiporters are disabled through
190:Alkaliphiles promise several interesting uses for
148:in respiring cells and to some extent through an
300:
298:
296:
210:; xylanases; pectinases; chitinases and their
127:has been observed to contain higher levels of
390:
8:
38:that require high salt content to survive).
538:
397:
383:
375:
173:Differences in alkaliphilic ATP production
292:
111:ions, and allowing for the uptake of
75:Mechanisms of cytosolic acidification
7:
14:
716:Acidophiles in acid mine drainage
238:Examples of alkaliphiles include
186:Applications and future research
63:and inactivation of cytosolic
1:
83:composed of residues such as
214:, including: 2-phenylamine;
202:; starch-degrading enzymes;
59:of DNA, instability of the
857:
701:Abiogenic petroleum origin
634:Thermococcus gammatolerans
241:Halorhodospira halochloris
253:Thiohalospira alkaliphila
552:Chloroflexus aurantiacus
146:electron transport chain
675:Halicephalobus mephisto
668:Paralvinella sulfincola
654:Cyanidioschyzon merolae
559:Deinococcus radiodurans
29:capable of survival in
247:Natronomonas pharaonis
51:
42:Background information
836:Biochemical reactions
661:Galdieria sulphuraria
590:Spirochaeta americana
355:John Wiley & Sons
49:
583:Thermus thermophilus
782:Radiotrophic fungus
759:Helaeomyia petrolei
706:Acidithiobacillales
615:Pyrococcus furiosus
180:proton-motive force
135:as compared to its
119:. In addition, the
357:. pp. 76–79.
52:
818:
817:
765:Hydrothermal vent
689:
688:
627:Pyrolobus fumarii
576:Thermus aquaticus
364:978-1-118-10300-5
349:Singh OV (2012).
85:galacturonic acid
848:
721:Archaeoglobaceae
694:Related articles
539:
519:Thermoacidophile
514:Hyperthermophile
490:Polyextremophile
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392:
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305:
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226:derivatives and
123:in alkaliphilic
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855:
851:
850:
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847:
846:
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821:
820:
819:
814:
805:Thermostability
741:Grylloblattidae
711:Acidobacteriota
685:
639:
600:
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470:Metallotolerant
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105:plasma membrane
101:phosphoric acid
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61:plasma membrane
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22:are a class of
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11:
5:
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736:Thermoproteota
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505:Radioresistant
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455:Lithoautotroph
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117:hydronium ions
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841:Extremophiles
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752:Halobacterium
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535:extremophiles
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406:Extremophiles
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228:organic acids
225:
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201:
197:
193:
192:biotechnology
185:
183:
181:
172:
170:
168:
164:
159:
155:
151:
147:
143:
138:
134:
130:
126:
122:
121:peptidoglycan
118:
114:
110:
106:
102:
98:
97:aspartic acid
94:
93:glutamic acid
90:
89:gluconic acid
86:
82:
74:
72:
70:
66:
62:
58:
48:
41:
39:
36:
32:
28:
25:
24:extremophilic
21:
831:Alkaliphiles
810:Thermotogota
797:
771:Methanopyrus
769:
757:
750:
746:Halobacteria
726:Berkeley Pit
681:Pompeii worm
673:
666:
659:
652:
632:
625:
613:
588:
581:
574:
565:Deinococcota
557:
550:
512: /
500:Psychrophile
424:
350:
344:
334:
325:
276:Extremophile
251:
245:
239:
237:
220:siderophores
189:
176:
163:neutrophilic
156:cells. This
154:fermentative
137:neutrophilic
124:
78:
57:denaturation
53:
20:Alkaliphiles
19:
18:
777:Movile Cave
731:Blood Falls
510:Thermophile
495:Psammophile
425:Alkaliphile
281:Neutrophile
224:cholic acid
216:carotenoids
212:metabolites
198:: alkaline
142:antiporters
133:amino acids
129:hexosamines
125:B. subtilis
825:Categories
800:polymerase
792:Tardigrade
621:Strain 121
485:Piezophile
475:Oligotroph
465:Methanogen
460:Lithophile
430:Capnophile
420:Acidophile
287:References
271:Acidophobe
266:Acidophile
204:cellulases
787:Rio Tinto
645:Eukaryota
524:Xerophile
480:Osmophile
450:Lipophile
440:Halophile
200:proteases
109:hydroxide
570:Snottite
543:Bacteria
445:Hypolith
435:Endolith
260:See also
234:Examples
167:mutation
81:polymers
31:alkaline
27:microbes
606:Archaea
533:Notable
208:lipases
196:enzymes
69:cytosol
65:enzymes
596:GFAJ-1
361:
339:Print.
250:, and
158:proton
150:ATPase
113:sodium
99:, and
413:Types
359:ISBN
131:and
115:and
798:Taq
152:in
827::
353:.
309:^
295:^
256:.
244:,
222:;
218:;
206:;
95:,
91:,
87:,
35:pH
398:e
391:t
384:v
367:.
33:(
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