An Extreme Thermophile,<i>Thermus thermophilus</i>, Is a Polyploid Bacterium

Ohtani, Naoto; Tomita, Masaru; Itaya, Mitsuhiro

doi:10.1128/jb.00662-10

Cited by 88 publications

(81 citation statements)

References 47 publications

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“…Polyploidy was also reported for Eubacteria such as Thermus thermophilus (4-5 genome copies; Ohtani et al, 2010) and for the halophilic archaeon Halobacterium volcanii with B18 genome copies per cell, a number which was downregulated to 10 genome copies per cell when H. volcanii entered stationary phase (Breuert et al, 2006). Here we report that the chromosomal content of akinetes in the cyanobacterium A. ovalisporum may accumulate to a maximum of 450 copies.…”

Section: Genome and Ribosome Multiplication In Akinetes A Sukenik Et Almentioning

confidence: 82%

Massive multiplication of genome and ribosomes in dormant cells (akinetes) of Aphanizomenon ovalisporum (Cyanobacteria)

et al. 2011

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Akinetes are dormancy cells commonly found among filamentous cyanobacteria, many of which are toxic and/or nuisance, bloom-forming species. Development of akinetes from vegetative cells is a process that involves morphological and biochemical modifications. Here, we applied a single-cell approach to quantify genome and ribosome content of akinetes and vegetative cells in Aphanizomenon ovalisporum (Cyanobacteria). Vegetative cells of A. ovalisporum were naturally polyploid and contained, on average, eight genome copies per cell. However, the chromosomal content of akinetes increased up to 450 copies, with an average value of 119 genome copies per akinete, 15-fold higher than that in vegetative cells. On the basis of fluorescence in situ hybridization, with a probe targeting 16S rRNA, and detection with confocal laser scanning microscopy, we conclude that ribosomes accumulated in akinetes to a higher level than that found in vegetative cells. We further present evidence that this massive accumulation of nucleic acids in akinetes is likely supported by phosphate supplied from inorganic polyphosphate bodies that were abundantly present in vegetative cells, but notably absent from akinetes. These results are interpreted in the context of cellular investments for proliferation following a long-term dormancy, as the high nucleic acid content would provide the basis for extended survival, rapid resumption of metabolic activity and cell division upon germination.

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Section: Genome and Ribosome Multiplication In Akinetes A Sukenik Et Almentioning

confidence: 82%

Massive multiplication of genome and ribosomes in dormant cells (akinetes) of Aphanizomenon ovalisporum (Cyanobacteria)

et al. 2011

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“…Increasing the chromosomal copy number in D. radiodurans does not enhance radiation resistance (241). In fact, many radiationsensitive bacterial species have multiple genome copies, such as M. luteus, Micrococcus sodonensis (435), Azotobacter vinelandii (379), and T. thermophilus (469). Chromosome multiplicity enhances radiation resistance in E. coli and S. cerevisiae, with the former being more radiation resistant when grown in rich medium, which gives rise to multigenomic cells (327), and the latter being more radiation resistant in the diploid than in the haploid form (433).…”

Section: Recombinational Processes In D Radiodurans Dna Repairmentioning

confidence: 99%

Oxidative Stress Resistance inDeinococcus radiodurans

Slade

Radman

2011

Microbiol Mol Biol Rev

646

639

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SUMMARY Deinococcus radiodurans is a robust bacterium best known for its capacity to repair massive DNA damage efficiently and accurately. It is extremely resistant to many DNA-damaging agents, including ionizing radiation and UV radiation (100 to 295 nm), desiccation, and mitomycin C, which induce oxidative damage not only to DNA but also to all cellular macromolecules via the production of reactive oxygen species. The extreme resilience of D. radiodurans to oxidative stress is imparted synergistically by an efficient protection of proteins against oxidative stress and an efficient DNA repair mechanism, enhanced by functional redundancies in both systems. D. radiodurans assets for the prevention of and recovery from oxidative stress are extensively reviewed here. Radiation- and desiccation-resistant bacteria such as D. radiodurans have substantially lower protein oxidation levels than do sensitive bacteria but have similar yields of DNA double-strand breaks. These findings challenge the concept of DNA as the primary target of radiation toxicity while advancing protein damage, and the protection of proteins against oxidative damage, as a new paradigm of radiation toxicity and survival. The protection of DNA repair and other proteins against oxidative damage is imparted by enzymatic and nonenzymatic antioxidant defense systems dominated by divalent manganese complexes. Given that oxidative stress caused by the accumulation of reactive oxygen species is associated with aging and cancer, a comprehensive outlook on D. radiodurans strategies of combating oxidative stress may open new avenues for antiaging and anticancer treatments. The study of the antioxidation protection in D. radiodurans is therefore of considerable potential interest for medicine and public health.

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“…In eukaryotes, homologous recombination normally takes place between sister chromatids (16). Moreover, in bacteria, such as Deinococcus radiodurans, HR can occur with one of the multiple copies of its genome; they thereby accomplish a high level of resistance to radiation (17). As Sulfolobus cells are predominantly present in G 2 phase (18), most of the time there is a second copy of the chromosome to repair DSBs via HR.…”

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confidence: 99%

DNA Processing Proteins Involved in the UV-Induced Stress Response of Sulfolobales

Wolferen

Albers

2015

J Bacteriol

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The ups operon of Sulfolobus species is highly induced upon UV stress. Previous studies showed that the pili encoded by this operon are involved in cellular aggregation, which is essential for subsequent DNA exchange between cells, resulting in homologous recombination. The presence of this pilus system increases the fitness of Sulfolobus cells under UV light-induced stress conditions, as the transfer of DNA takes place in order to repair UV-induced DNA lesions via homologous recombination. Four conserved genes (saci_1497 to saci_1500) which encode proteins with putative DNA processing functions are present downstream of the ups operon. In this study, we show that after UV treatment the cellular aggregation of strains with saci_1497, saci_1498, and saci_1500 deletions is similar to that of wild-type strains; their survival rates, however, were reduced and similar to or lower than those of the pilus deletion strains, which could not aggregate anymore. DNA recombination assays indicated that saci_1498, encoding a ParB-like protein, plays an important role in DNA transfer. Moreover, biochemical analysis showed that the endonuclease III encoded by saci_1497 nicks UV-damaged DNA. In addition, RecQ-like helicase Saci_1500 is able to unwind homologous recombination intermediates, such as Holliday junctions. Interestingly, a saci_1500 deletion mutant was more sensitive to UV light but not to the replication-stalling agents hydroxyurea and methyl methanesulfonate, suggesting that Saci_1500 functions specifically in the UV damage pathway. Together these results suggest a role of Saci_1497 to Saci_1500 in the repair or transfer of DNA that takes place after UV-induced damage to the genomic DNA of Sulfolobus acidocaldarius. IMPORTANCESulfolobales species increase their fitness after UV stress by a UV-inducible pilus system that enables high rates of DNA exchange between cells. Downstream of the pilus operon, three genes that seem to play a role in the repair or transfer of the DNA between Sulfolobus cells were identified, and their possible functions are discussed. Next to the previously described role of UV-inducible pili in the exchange of DNA, we have thereby increased our knowledge of DNA transfer at the level of DNA processing. This paper therefore contributes to the overall understanding of the DNA exchange mechanism among Sulfolobales cells. In all domains of life, DNA repair is crucial for maintenance of genome integrity upon exposure to intra-or extracellular DNAdamaging threats (1). Unlike DNA repair in bacteria, archaeal DNA repair and its regulation are still far from well understood (1, 2). Homology searches revealed that the proteins in archaeal DNA repair pathways show similarities to both bacterial and eukaryotic proteins. In addition, DNA repair proteins with unique archaeal features exist (3).Previously, it was speculated that archaea might have SOS-like responses similar to those in certain bacteria (4); however, microarray studies revealed that neither Haloarchaea (5, 6) nor Sulfolobus species (7...

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An Extreme Thermophile,Thermus thermophilus, Is a Polyploid Bacterium

Cited by 88 publications

References 47 publications

Massive multiplication of genome and ribosomes in dormant cells (akinetes) of Aphanizomenon ovalisporum (Cyanobacteria)

Massive multiplication of genome and ribosomes in dormant cells (akinetes) of Aphanizomenon ovalisporum (Cyanobacteria)

Oxidative Stress Resistance inDeinococcus radiodurans

DNA Processing Proteins Involved in the UV-Induced Stress Response of Sulfolobales

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