halocin

Halocins are bacteriocins produced by halophilic Archaea{{cite journal |vauthors=Li Y, Xiang H, Tan H |title=[Halocin: protein antibiotics produced by extremely halophilic archaea] |language=zh |journal=Wei Sheng Wu Xue Bao |volume=42 |issue=4 |pages=502–5 |date=2002 |pmid=12557560 }}{{cite journal |vauthors=O'Connor EM, Shand RF |title=Halocins and sulfolobicins: the emerging story of archaeal protein and peptide antibiotics |journal=Journal of Industrial Microbiology & Biotechnology |volume=28 |issue=1 |pages=23–31 |date=2002 |pmid=11938468 |doi=10.1038/sj/jim/7000190|s2cid=16583426 |doi-access=free }} and a type of archaeocin.{{cite book |chapter-url=http://www.horizonpress.com/arch|vauthors=Shand RF, Leyva KJ |date=2008|chapter=Archaeal Antimicrobials: An Undiscovered Country|title=Archaea: New Models for Prokaryotic Biology|publisher=Caister Academic Press|isbn=978-1-904455-27-1}}

Since their discovery in 1982,{{cite journal |vauthors=Rodríguez-Valera F, Juez G, Kushner DJ |title=Halocins: salt-dependent bacteriocins produced by extremely halophilic rod |journal=Canadian Journal of Microbiology |volume=28 |pages=151–154 |date=1982 |doi=10.1139/m82-019}} halocins have been demonstrated to be diverse in a similar ways as the other bacteriocins.{{cite journal |vauthors=Torreblanca M, Meseguer I, Rodríguez-Valera F |title=Halocin H6, a bacteriocin from Haloferax gibbonsii |journal=Journal of General Microbiology |volume=135 |issue=10 |pages=2655–2661 |date=1989 |doi=10.1099/00221287-135-10-2655|doi-access=free }}{{cite journal |vauthors=Price LB, Shand RF |title=Halocin S8: a 36-Amino-Acid Microhalocin from the Haloarchaeal Strain S8a |journal=Journal of Bacteriology |volume=182 |issue=17 |pages=4951–8 |date=2000 |pmid=10940040 |doi=10.1128/JB.182.17.4951-4958.2000 |pmc=111376}}{{cite journal |vauthors=Platas G, Meseguer I, Amils R |title=Purification and biological characterization of halocin H1 from Haloferax mediterranei M2a |journal=International Microbiology |volume=5 |issue=1 |pages=15–9 |date=2002 |pmid=12102231 |doi=10.1007/s10123-002-0053-4|s2cid=45501770 |url=http://revistes.iec.cat/index.php/IM/article/view/9346 }} Some are large proteins, some small polypeptides (microhalocins). This diversity is surprising for a number of reasons, including the original presumptions that Archaea, particularly extremophiles, live at relatively low densities under conditions that may not require antagonistic behavior.

The genetics,{{cite journal |vauthors=Mei SS, Li Y, Lu QH, Xiang H |title=[Cloning and analysis of genes in the halocin C8 gene cluster] |language=zh |journal=Wei Sheng Wu Xue Bao |volume=46 |issue=2 |pages=318–22 |date=2006 |pmid=16736600 }}{{cite journal |vauthors=Sun C, Li Y, Mei S, Lu Q, Zhou L, Xiang H |title=A single gene directs both production and immunity of halocin C8 in a haloarchaeal strain AS7092 |journal=Molecular Microbiology |volume=57 |issue=2 |pages=537–49 |date=2005 |pmid=15978083 |doi=10.1111/j.1365-2958.2005.04705.x|doi-access=free }}{{cite book | last = Perez | first = AM | title = Growth physiology of Haloferax mediterranei R4 and purification of halocin H4 | publisher = Northern Arizona University | date = 2000 | location = Flagstaff, Arizona | pages = Masters Thesis }}{{cite journal |vauthors=Cheung J, Danna KJ, O'Connor EM, Price LB, Shand RF |title=Isolation, sequence, and expression of the gene encoding halocin H4, a bacteriocin from the halophilic archaeon Haloferax mediterranei R4 |journal=Journal of Bacteriology |volume=179 |issue=2 |pages=548–51 |date=1997 |pmid=8990311 |doi= 10.1128/jb.179.2.548-551.1997|pmc=178729}}{{cite journal |vauthors=Platas G, Meseguer I, Amils R |title=Optimization of the production of a bacteriocin from Haloferax mediterranei Xia3 |journal=Microbiología |volume=12 |issue=1 |pages=75–84 |date=1996 |pmid=9019137 }} mechanism of production{{cite journal |vauthors=Meseguer I, Rodríguez-Valera F |title=Production and purification of halocin H4 |journal=FEMS Microbiology Letters |volume=28 |pages=177–182 |date=1985 |doi=10.1111/j.1574-6968.1985.tb00787.x |issue=2|doi-access=free }}{{cite journal |vauthors=Li Y, Xiang H, Liu J, Zhou M, Tan H |title=Purification and biological characterization of halocin C8, a novel peptide antibiotic from Halobacterium strain AS7092 |journal=Extremophiles |volume=7 |issue=5 |pages=401–7 |date=2003 |pmid=12811620 |doi=10.1007/s00792-003-0335-6|s2cid=32609554 }} and mechanism of action{{cite book |author=Platas G |title=Caracterizacíon de la actividad antimicrobiana de la haloarquea Haloferax mediterranei Xia3 |publisher=Universidad Autónoma de Madrid |location=Madrid, Spain |date=1995 |pages = Doctoral Thesis}}{{cite journal |vauthors=Meseguer I, Torreblanca M, Konishi T |title=Specific inhibition of the halobacterial Na+/H+ antiporter by halocin H6 |journal=Journal of Biological Chemistry |volume=270 |issue=12 |pages=6450–5 |date=1995 |pmid=7896778 |doi=10.1074/jbc.270.12.6450|doi-access=free }}{{cite journal |vauthors=Meseguer I, Rodríguez-Valera F |title= Effect of halocin H4 on cells of Halobacterium halobium |journal=Journal of General Microbiology |volume=132 |issue= 11 |pages=3061–3068 |date=1986 |doi=10.1099/00221287-132-11-3061|doi-access=free }}{{cite journal |vauthors=Girones F, Minagawa A, Hatano Y, Torreblanca M, Meseguer I, Sanchez M, Konishi T |journal=Nippon Yakugakkai Nenkai Koen Yoshishu |volume=121 |issue=4 |pages=116 |date=2001 |title=Protein-protein interaction between halocin H7 and halobacterial membrane protein}} of the halocins have been studied, but not exhaustively. The ecology of the halocins{{cite journal |vauthors=Kis-Papo T, Oren A |title=Halocins: are they involved in the competition between halobacteria in saltern ponds? |journal=Extremophiles |volume=4 |issue=1 |pages=35–41 |date=2000 |pmid=10741835 |doi=10.1007/s007920050005|s2cid=24584604 }}{{cite journal |vauthors=Meseguer I, Rodríguez-Valera F, Ventosa A |title=Antagonistic interactions among halobacteria due to halocin production |journal=FEMS Microbiology Letters |volume=36 |pages=177–182 |date=1986 |doi=10.1111/j.1574-6968.1986.tb01691.x |issue=2–3|doi-access=free }}{{cite journal |author=Oren A |title=The ecology of the halophilic archaea |journal=FEMS Microbiology Reviews |volume=13 |pages=415–440 |date=1994 |doi=10.1111/j.1574-6976.1994.tb00060.x |issue=4|doi-access=free }} has been investigated as well. One interesting observation is that the halocins are active across the major divisions of archaea,{{cite journal |vauthors=Haseltine C, Hill T, Montalvo-Rodriguez R, Kemper SK, Shand RF, Blum P |title=Secreted Euryarchaeal Microhalocins Kill Hyperthermophilic Crenarchaea |journal=Journal of Bacteriology |volume=183 |issue=1 |pages=287–91 |date=2001 |pmid=11114928 |doi=10.1128/JB.183.1.287-291.2001 |pmc=94877}} thus violating the dogma that they should be most effective against the most closely related strains.

Halocins are particularly interesting because of the way the pore-forming bacteriocins have been used to probe cell membrane structure and the production and maintenance of energetic ion gradients across the membrane. The halophiles live at such extreme ion concentrations that they represent a set of unusual solutions and adaptations with regard to their energetic gradients. The ability to use native halocins to study these gradients provides a motivation for their characterization.

They may have a role in human medicine.{{cite journal |title=Halocin H7 decreases infarct size and ectopic beats after mycardial reperfusion in dogs |journal=Journal of Physiology |date=1998 |vauthors=Alberola A, Meseguer I, Torreblanca M, Moya A, Sancho S, Polo B, Soria B, Such L }}{{cite journal |vauthors=Lequerica JL, O'Connor JE, Such L, Alberola A, Meseguer I, Dolz M, Torreblanca M, Moya A, Colom F, Soria B |title=A halocin acting on Na+/H+ exchanger of haloarchaea as a new type of inhibitor in NHE of mammals |journal=Journal of Physiology and Biochemistry |volume=62 |issue=4 |pages=253–62 |date=2006 |pmid=17615951 |doi=10.1007/BF03165754|s2cid=8822522 }}

They are also found in many of the type species that are used to learn about halophiles in general.{{cite journal |vauthors=Soppa J, Oesterhelt D |title=Halobacterium sp. GRB: a species to work with!? |journal=Canadian Journal of Microbiology |volume=35 |issue=1 |pages=205–9 |date=1989 |pmid=2720494 |doi=10.1139/m89-032}}

Like other bacteriocins, the halocins are under investigation as antimicrobials for use in controlling spoilage during industrial processes; in this case, leather production.{{cite journal |vauthors=Birbir M, Eryilmaz S, Ogan A |journal=Journal of the Society of Leather Technologists and Chemists |volume=88 |issue=3 |pages=99–104 |date=2004 |title=Prevention of halophilic microbial damage on brine cured hides by extremely halophilic halocin producer strains}}

Because the literature about halocins is relatively circumscribed, it can be exhaustively cited. Several times they have been addressed in book chapters.{{cite book |vauthors=Rdest U, Sturm M |editor=Burgess R |chapter=Bacteriocins from halobacteria |title=Protein Purification: Micro to Macro |pages=271–278 |publisher=Alan R. Liss |location=New York, New York |date=1987}}{{cite book |vauthors=Shand RF, Perez AM |editor=Seckback J |chapter=Haloarchaeal growth physiology |title=Enigmatic Organisms and Life in Extreme Environments |pages=413–424 |publisher=Kluwer Acadademic Press |location=Dordrecht, The Netherlands |date=1999}}{{cite book |vauthors=Shand RF, Price LB, O'Connor EM |editor=Oren A |chapter=Halocins: protein antibiotics from hypersaline environments |title=Microbiology and Biogeochemistry of Hypersaline Environments |pages=295–306 |publisher=CRC Press |date=1999 |location=Boca Raton, FL}}

BACTIBASE{{cite journal |title=BACTIBASE: a new web-accessible database for bacteriocin characterization |vauthors=Hammami R, Zouhir A, Ben Hamida J, Fliss I |journal=BMC Microbiology |date=2007 |volume=7 |pages=89 |pmid=17941971 |doi=10.1186/1471-2180-7-89 |pmc=2211298 |doi-access=free }}{{cite journal |title=BACTIBASE second release: a database and tool platform for bacteriocin characterization |vauthors=Hammami R, Zouhir A, Le Lay C, Ben Hamida J, Fliss I |journal=BMC Microbiology |date=2010 |volume=10 |pages=22 |pmid=20105292 |doi=10.1186/1471-2180-10-22 |pmc=2824694 |doi-access=free }} database is an open-access database for bacteriocins including halocins ([http://bactibase.hammamilab.org/bacteriocinslist.php?Name=halocin view complete list]).