Topic
Halocin
About: Halocin is a research topic. Over the lifetime, 53 publications have been published within this topic receiving 1372 citations.
Papers published on a yearly basis
Papers
TL;DR: Archaeocins are produced by the hyperthermophile “Sulfolobus islandicus” and are associated with small particles apparently derived from the cell's S-layer, leaving their mechanism(s) of action mostly a mystery.
Abstract: Production of antibiotic peptides and proteins is a near-universal feature of living organisms regardless of phylogenetic classification. Bacteriocins (proteinaceous antimicrobials from the domain Bacteria) have been studied for over 75 years, and the eucaryocins (proteinaceous antimicrobials from the domain Eucarya) since the early 1960s. However, one domain of organisms, the Archaea, containing hyperthermophiles, extreme halophiles and the methanogens, is just beginning to be scrutinized for the production of peptide antibiotics. Production of archaeal proteinaceous antimicrobials (archaeocins) from extreme halophiles (halocins) is a nearly universal feature of the rod-shaped haloarchaea. Halocin activity is first detectable in culture supernatants at the beginning of the transition into stationary phase, concomitant with an induction of transcription of the structural gene. Halocins are diverse in size, consisting of proteins as large as 35 kDa and peptide “microhalocins” as small as 3.6 kDa. The 36 amino acids of microhalocin HalS8 are located in the interior of a 311-residue pro-protein from which they are liberated by an unknown mechanism. Microhalocins are hydrophobic and robust, withstanding heat, desalting and exposure to organic solvents. Unlike the peptide bacteriocins and the eucaryocins, microhalocins possess a large number of neutral residues and are not cationic, leaving their mechanism(s) of action mostly a mystery. While microhalocins affect a variety of haloarchaeal genera (kingdom Euryarchaeota), they also exhibit cross-kingdom toxicity, inhibiting or killing Sulfolobus species (kingdom Crenarchaeota). Finally, archaeocins also are produced by the hyperthermophile “Sulfolobus islandicus”. These 20-kDa protein antibiotics are not excreted into the environment, but are associated with small particles apparently derived from the cell's S-layer. Journal of Industrial Microbiology & Biotechnology (2002) 28, 23–31 DOI: 10.1038/sj/jim/7000190
132 citations
TL;DR: The first gene to encode a haloarchaeal bacteriocin (halocin H4) has been cloned and sequenced from Haloferax mediterranei R4 and both the signal sequence in the halocIn H4 preprotein and the monocistronic halH4 gene have some unusual features.
Abstract: The first gene to encode a haloarchaeal bacteriocin (halocin H4) has been cloned and sequenced from Haloferax mediterranei R4. Both the signal sequence in the halocin H4 preprotein and the monocistronic halH4 gene have some unusual features. The physiology of halH4 expression reveals that although halH4 transcripts are present at low basal levels during exponential growth, halocin H4 activity first appears as the culture enters stationary phase. As halocin activity levels increase, so do transcript levels, but then activity levels decrease precipitously while transcript levels remain elevated.
93 citations
TL;DR: The results show that halocin production should be considered as a practically general feature of halobacteria and many different halocins are produced by this heterogeneous group of micro‐organisms.
Abstract: Antagonisms among members of nine phenons of halobacteria were detected by combining two methods based on the double layer technique. Inhibitory activities were not due to phages. The protein nature of the inhibitors indicated that they were halocins. With only one exception, all strains tested exhibited inhibitory activity against other halobacteria due to the production of halocins. A very wide range of activity spectra was detected and the numerical comparative analysis showed little grouping, due to the scarce similarities between them. This indicates that many different halocins are produced by this heterogeneous group of micro-organisms. Our results show that halocin production should be considered as a practically general feature of halobacteria.
87 citations
TL;DR: Encoding of the halS8 gene is encoded on an ∼200-kbp megaplasmid and contains a 933-bp open reading frame, of which 108 bp are occupied by halocin S8, the first microhalocin to be described.
Abstract: Halocin S8 is a hydrophobic microhalocin of 36 amino acids (3,580 Da) and is the first microhalocin to be described. This peptide antibiotic is unique since it is processed from inside a much larger, 33,962-Da pro-protein. Halocin S8 is quite robust, as it can be desalted, boiled, subjected to organic solvents, and stored at 4°C for extended periods without losing activity. The complete amino acid sequence of halocin S8 was obtained first by Edman degradation of the purified protein and verified from the halS8 gene: H2N-S-D-C-N-I-N-S-N-T-A-A-D-V-I-L-C-F-N-Q-V-G-S-C-A-L-C-S-P-T-L-V-G-G-P-V-P-COOH. The halS8 gene is encoded on an ∼200-kbp megaplasmid and contains a 933-bp open reading frame, of which 108 bp are occupied by halocin S8. Both the halS8 promoter and the “leaderless” halS8 transcript are typically haloarchaeal. Northern blot analysis revealed three halS8 transcripts: two abundant and one minor. Inspection of the 3′ end of the gene showed only a single, weak termination site (5′-TTTAT-3′), suggesting that some processing of the larger transcripts may be involved. Expression of the halS8 gene is growth stage dependent: basal halS8 transcript levels are present in low concentrations during exponential growth but increase ninefold during the transition to stationary phase. Initially, halocin activity parallels halS8 transcript levels very closely. However, when halocin activity plateaus, transcripts remain abundant, suggesting inhibition of translation at this point. Once the culture enters stationary phase, transcripts rapidly return to basal levels.
82 citations
TL;DR: This review summarizes the present knowledge on halocins and sulfolobicins, the two classes of archaeocins that have been evidenced until now, and brings light on aspects of emerging research such as their ecological role or potential applications.
78 citations
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2021 | 1 |
| 2020 | 3 |
| 2019 | 2 |
| 2018 | 3 |
| 2017 | 6 |
| 2016 | 3 |