Archaeocin

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Archaeocin is the name given to a new type of potentially useful antibiotic that is derived from the Archaea group of organisms. [1] Eight archaeocins have been partially or fully characterized, but hundreds of archaeocins are believed to exist, especially within the haloarchaea. Production of these archaeal proteinaceous antimicrobials is a nearly universal feature of the rod-shaped haloarchaea. [2]

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The prevalence of archaeocins from other members of this domain is unknown simply because no one has looked for them. The discovery of new archaeocins hinges on recovery and cultivation of archaeal organisms from the environment. For example, samples from a novel hypersaline field site, Wilson Hot Springs in the Fish Springs National Wildlife Refuge in eastern Utah, [3] recovered 350 halophilic organisms; preliminary analysis of 75 isolates showed that 48 were archaeal and 27 were bacterial. [4]

Halocins

Halocins are classified as either peptide (≤ 10 kDa; 'microhalocins') or protein (> 10 kDa) antibiotics produced by members of the archaeal family Halobacteriaceae. To date, all of the known halocin genes are encoded on megaplasmids (> 100 kbp) and possess typical haloarcheal TATA and BRE promoter regions. Halocin transcripts are leaderless and the translated preproteins or preproproteins are most likely exported using the twin arginine translocation (Tat) pathway, as the Tat signal motif (two adjacent arginine residues) is present within the amino terminus. Halocin genes are almost universally expressed at the transition between exponential and stationary phases of growth; the only exception is halocin H1, which is induced during exponential phase. In contrast, the larger halocin proteins are heat-labile and typically obligately halophilic as they lose their activity (or activity is reduced) when desalted.[ citation needed ]

Microhalocins, peptide halocins

Currently, five peptide halocins have been partially or completely characterized at the protein and/or genetic levels: HalS8, HalR1, HalC8, HalH7, and HalU1. These antimicrobial peptides range from ~3 to 7.4 kDa in molecular mass, consisting of 36 to 76 amino acid residues. Two of the microhalocins (HalS8 and HalC8) are produced by proteolytic cleavage from a larger preproprotein by an unknown mechanism. Microhalocins are hydrophobic peptides that remain active even if desalted and/or stored at 4 °C and are fairly insensitive to heat and organic solvents. The first microhalocin to be characterized was HalS8, [5] produced by the uncharacterized haloarchaeon S8a isolated from the Great Salt Lake, UT, USA. [4]

Protein halocins

Two can be classified as protein halocins: HalH1 and HalH4; the molecular masses of the remaining halocins have yet to be elucidated. Halocin H1 is produced by Hfx. mediterranei M2a (formerly strain Xia3), isolated from a solar saltern near Alicante, Spain. It is a 31 kDa protein that is heat-labile, loses activity when desalted, and exhibits a broad range of inhibition within the haloarchaea. Halocin H1 has yet to be characterized at the protein and genetic levels. In contrast, HalH4, produced by Hfx. mediterranei R4 (ATCC 33500), also isolated from a solar saltern near Alicante, Spain was the first halocin discovered. [6] The molecular mass of the mature HalH4 protein is 34.9 kDa (359 amino acids), processed from a preprotein of 39.6 kDa; the mechanism for processing is unknown. Halocin H4 is an archaeolytic halocin and adsorbs to sensitive Hbt. salinarum cells where it may be disrupting membrane permeability. [4]

Sulfolobicins

The archaeocins produced by Sulfolobus are entirely different from halocins, since their activity is predominantly associated with the cells and not the supernatant. To date, the spectrum of sulfolobicin activity appears to be restricted to other members of the Sulfolobales: the sulfolobicin inhibited S. solfataricus P1, S. shibatae B12, and six nonproducing strains of S. islandicus. Activity appears to be archaeocidal but not archaeolytic. [4] Two genes involved in sulfolobicin production have been identified in S. acidocaldarius and S. tokodaii. The sulfolobicins appear to represent a novel class of antimicrobial proteins. [7]

See also

Related Research Articles

<i>Sulfolobus</i> Genus of archaea

Sulfolobus is a genus of microorganism in the family Sulfolobaceae. It belongs to the archaea domain.

<span class="mw-page-title-main">Haloarchaea</span> Class of salt-tolerant archaea

Haloarchaea are a class of the Euryarchaeota, found in water saturated or nearly saturated with salt. Halobacteria are now recognized as archaea rather than bacteria and are one of the largest groups. The name 'halobacteria' was assigned to this group of organisms before the existence of the domain Archaea was realized, and while valid according to taxonomic rules, should be updated. Halophilic archaea are generally referred to as haloarchaea to distinguish them from halophilic bacteria.

Cathelicidin antimicrobial peptide (CAMP) is a polypeptide that is primarily stored in the lysosomes of macrophages and polymorphonuclear leukocytes (PMNs); in humans, the CAMP gene encodes the peptide precursor CAP-18, which is processed by proteinase 3-mediated extracellular cleavage into the active form LL-37. LL-37 is the only peptide in the Cathelicidin family found in the human body.

<span class="mw-page-title-main">Sulfolobales</span> Order of archaea

In taxonomy, the Sulfolobales are an order of the Thermoprotei.

<span class="mw-page-title-main">Sulfolobaceae</span> Family of archaea

Sulfolobaceae are a family of the Sulfolobales belonging to the domain Archaea. The family consists of several genera adapted to survive environmental niches with extreme temperature and low pH conditions.

<span class="mw-page-title-main">Lysin</span>

Lysins, also known as endolysins or murein hydrolases, are hydrolytic enzymes produced by bacteriophages in order to cleave the host's cell wall during the final stage of the lytic cycle. Lysins are highly evolved enzymes that are able to target one of the five bonds in peptidoglycan (murein), the main component of bacterial cell walls, which allows the release of progeny virions from the lysed cell. Cell-wall-containing Archaea are also lysed by specialized pseudomurein-cleaving lysins, while most archaeal viruses employ alternative mechanisms. Similarly, not all bacteriophages synthesize lysins: some small single-stranded DNA and RNA phages produce membrane proteins that activate the host's autolytic mechanisms such as autolysins.

<span class="mw-page-title-main">Prokaryotic large ribosomal subunit</span>

50S is the larger subunit of the 70S ribosome of prokaryotes, i.e. bacteria and archaea. It is the site of inhibition for antibiotics such as macrolides, chloramphenicol, clindamycin, and the pleuromutilins. It includes the 5S ribosomal RNA and 23S ribosomal RNA.

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Halocins are bacteriocins produced by halophilic Archaea and a type of archaeocin.

<span class="mw-page-title-main">Archaea</span> Domain of single-celled organisms

Archaea is a domain of single-celled organisms. These microorganisms lack cell nuclei and are therefore prokaryotes. Archaea were initially classified as bacteria, receiving the name archaebacteria, but this term has fallen out of use.

<span class="mw-page-title-main">Branch migration</span>

Branch migration is the process by which base pairs on homologous DNA strands are consecutively exchanged at a Holliday junction, moving the branch point up or down the DNA sequence. Branch migration is the second step of genetic recombination, following the exchange of two single strands of DNA between two homologous chromosomes. The process is random, and the branch point can be displaced in either direction on the strand, influencing the degree of which the genetic material is exchanged. Branch migration can also be seen in DNA repair and replication, when filling in gaps in the sequence. It can also be seen when a foreign piece of DNA invades the strand.

<span class="mw-page-title-main">Affitin</span>

Affitins are artificial proteins with the ability to selectively bind antigens. They are structurally derived from the DNA binding protein Sac7d, found in Sulfolobus acidocaldarius, a microorganism belonging to the archaeal domain. By randomizing the amino acids on the binding surface of Sac7d and subjecting the resulting protein library to rounds of ribosome display, the affinity can be directed towards various targets, such as peptides, proteins, viruses, and bacteria.

An archaeosortase is a protein that occurs in the cell membranes of some archaea. Archaeosortases recognize and remove carboxyl-terminal protein sorting signals about 25 amino acids long from secreted proteins. A genome that encodes one archaeosortase may encode over fifty target proteins. The best characterized archaeosortase target is the Haloferax volcanii S-layer glycoprotein, an extensively modified protein with O-linked glycosylations, N-linked glycosylations, and a large prenyl-derived lipid modification toward the C-terminus. Knockout of the archaeosortase A (artA) gene, or permutation of the motif Pro-Gly-Phe (PGF) to Pro-Phe-Gly in the S-layer glycoprotein, blocks attachment of the lipid moiety as well as blocking removal of the PGF-CTERM protein-sorting domain. Thus archaeosortase appears to be a transpeptidase, like sortase, rather than a simple protease.

<i>Haloquadratum walsbyi</i> Species of archaeon

Haloquadratum walsbyi is of the genus Haloquadratum, within the archaea domain known for its square halophilic nature. First discovered in a brine pool in the Sinai peninsula of Egypt, H. walsbyi is noted for its flat, square-shaped cells, and its unusual ability to survive in aqueous environments with high concentrations of sodium chloride and magnesium chloride. The species' genus name Haloquadratum translates from Greek and Latin as "salt square". This archaean is also commonly referred to as "Walsby's Square Bacterium" because of its identifying square shape which makes it unique. In accordance with its name, Haloquadratum walsbyi are most abundantly observed in salty environments.

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Saccharolobus solfataricus is a species of thermophilic archaeon. It was transferred from the genus Sulfolobus to the new genus Saccharolobus with the description of Saccharolobus caldissimus in 2018.

Sulfolobus acidocaldarius is a thermoacidophilic archaeon that belongs to the phylum Thermoproteota. S. acidocaldarius was the first Sulfolobus species to be described, in 1972 by Thomas D. Brock and collaborators. This species was found to grow optimally between 75 and 80 °C, with pH optimum in the range of 2-3.

<span class="mw-page-title-main">Shiladitya DasSarma</span>

Shiladitya DasSarma is a molecular biologist well-known for contributions to the biology of halophilic and extremophilic microorganisms. He is a Professor in the University of Maryland Baltimore. He earned a PhD degree in Biochemistry from the Massachusetts Institute of Technology and a BS degree in Chemistry from Indiana University Bloomington. Prior to taking a faculty position, he conducted research at the Massachusetts General Hospital, Harvard Medical School, and Pasteur Institute, Paris.

<span class="mw-page-title-main">Archaeal virus</span>

An archaeal virus is a virus that infects and replicates in archaea, a domain of unicellular, prokaryotic organisms. Archaeal viruses, like their hosts, are found worldwide, including in extreme environments inhospitable to most life such as acidic hot springs, highly saline bodies of water, and at the bottom of the ocean. They have been also found in the human body. The first known archaeal virus was described in 1974 and since then, a large diversity of archaeal viruses have been discovered, many possessing unique characteristics not found in other viruses. Little is known about their biological processes, such as how they replicate, but they are believed to have many independent origins, some of which likely predate the last archaeal common ancestor (LACA).

References

  1. ↑ Blum P, ed. (2008). Archaea: New Models for Prokaryotic Biology. Caister Academic Press. ISBN   978-1-904455-27-1.
  2. ↑ O'Connor EM; Shand RF (2002). "Halocins and sulfolobicins: the emerging story of archaeal protein and peptide antibiotics". J. Ind. Microbiol. Biotechnol. 28 (1): 23–31. doi: 10.1038/sj/jim/7000190 . PMID   11938468. S2CID   16583426.
  3. ↑ Pete Polsgrove; Amy Fleishman Littlejohn; Barry Roberts; Richard F. Shand; Northern Arizona University (June 4–5, 2005). "Wilson Hot Springs - A Desert Hypersaline Salt Marsh Research Site". Archived from the original on 2008-12-17.
  4. 1 2 3 4 Shand RF; Leyva KJ (2008). "Archaeal Antimicrobials: An Undiscovered Country". Archaea: New Models for Prokaryotic Biology. Caister Academic Press. ISBN   978-1-904455-27-1.
  5. ↑ Price LB; Shand RF (2000). "Halocin S8: a 36-amino-acid microhalocin from the haloarchaeal strain S8a". J. Bacteriol. 182 (17): 4951–8. doi:10.1128/JB.182.17.4951-4958.2000. PMC   111376 . PMID   10940040.
  6. ↑ Cheung J; Danna KJ; O'Connor EM; Price LB; Shand RF (1997). "Isolation, sequence, and expression of the gene encoding halocin H4, a bacteriocin from the halophilic archaeon Haloferax mediterranei R4". J. Bacteriol. 179 (2): 548–51. doi:10.1128/jb.179.2.548-551.1997. PMC   178729 . PMID   8990311.
  7. ↑ Ellen AF; Rohulya OV; Fusetti F; Wagner M; Albers SV; Driessen AJ (2011). "The sulfolobicin genes of Sulfolobus acidocaldarius encode novel antimicrobial proteins". J. Bacteriol. 193 (17): 4380–87. doi:10.1128/jb.05028-11. PMC   3165506 . PMID   21725003.
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