Dynamic plasmid populations in Halobacterium halobium

Pfeifer, Felicitas; Blaseio, Ulrike; Ghahraman, Parvin

doi:10.1128/jb.170.8.3718-3724.1988

Cited by 28 publications

(20 citation statements)

References 15 publications

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“…In the natural environment, gas vesicles must confer a selective advantage upon H . salinarium since the p-vac gene cluster has not been lost despite the extremely high frequency of p-uac mutants (Pfeifer et al, 1988). …”

Section: Discussionmentioning

confidence: 99%

“…A second class of gas vesicle mutants consists of those that produce no gas vesicles (Gv-), presumably due to mutations within both p-vac and c-uac. Mutants affected in gas vesicle synthesis occur with a high frequency, reportedly up to 1 ' / t (Pfeifer et al, 1981), due mostly to insertions or deletions within p-uac (Pfeifer et al, 1988).…”

Section: Introductionmentioning

confidence: 99%

“…Such low oxygen concentrations are a consequence of the limited solubility of oxygen at high salt concentrations (Smith, 1928) and of respiration by micro-organisms present at high densities in these habitats (Rodriguez-Valera et al, 1985). H. salinarium is a facultative anaerobe: it can grow under microaerobic and anaerobic conditions by using alternative terminal electron acceptors (Oren, 1991) , by fermenting arginine (Hartmann et al, 1980), or by using light-driven ion pumps, such as bacteriorhodopsin (Oesterhelt & Stoeckenius, 1973 ;Rodriguez-Valera et al, 1983). In environments where there are steep gradients of oxygen concentration, however, gas vesicle production may provide an advantage to the halobacteria by allowing them to float to the brine surface, where aerobic respiration can occur, as Petter (1932) suggested.…”

Section: Introductionmentioning

confidence: 99%

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Growth competition between Halobacterium salinarium strain PHH1 and mutants affected in gas vesicle synthesis

1997

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To investigate the role of the buoyancy provided by gas vesicles in the facultative anaerobe Halobacterium salinarium PHHl, the growth of a gasvacuolate (Gv' ) strain in competition with two gas-vesicle-def ective ( G e mutants was examined. The Gv+ strain synthesized gas vesicles throughout its growth cycle, and floated up to form a thick surface scum during the exponential growth phase in static culture. Mutant GvM produced significantly fewer gas vesicles than the Gv+ strain in corresponding stages of growth, although in late stationary phase a small proportion of cells floated up to the surface of static cultures. Mutant Gvd& had a much lower gas vesicle content in shaken culture and produced negligible amounts of gas vesicles in static culture. The Gv+ and the two G f l strains grew equally well in shaken cultures, but in static cultures, where steep vertical gradients of oxygen concentration were established, Gvdefl was outgrown by the Gv* strain. Gd* outcompeted the Gv+ strain in shallow static cultures, perhaps because Gvdefz carried a smaller protein burden, which offset the benefits of buoyancy. This selection for Gvdefz was lost in deeper static cultures, although it could be restored by aerating static cultures from below. The results support the hypothesis that the role of buoyancy in halobacteria is to maintain cells at the more aerated surface of brine pools.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Growth competition between Halobacterium salinarium strain PHH1 and mutants affected in gas vesicle synthesis

1997

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“…and pHSB2, restriction analysis of the plasmid isolated from SB3 cells or of more than 30 clones from the pHSB-pUC19 library revealed no recombinants between pHSB1 and pHSB2. This is remarkable, given the high rate of recombination characteristic of several halobacterial strains (4,18), and suggests that hybrid plasmids are not stable.…”

Section: Gaggcc Cgcttccagagacgacgac Cgaphsb2 B a I D R F Q 8 W Y D D mentioning

confidence: 99%

Heterogeneity of small plasmids from halophilic archaea

1993

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Small multicopy plasmids in three strains of halophilic archaea, SB3, GRB, and GN101, were found to be present in a cell as a population of related but not identical sequences. Two types of heterogeneity were observed: macroheterogeneity, represented by two major plasmid sequence versions homologous to each other by 80%o, and microheterogeneity, in which individual plasmids differ by one or a few nucleotide substitutions.Plasmids are self-replicating extrachromosomal genetic elements present in a cell in multiple copies. Usually, all copies of the same plasmid have the same nucleotide sequence. Similar but not identical plasmids generated by mutation are normally incompatible and rapidly segregate so that eventually only one plasmid variant is found in the cell culture (for reviews, see references 3 and 17).The presence of extrachromosomal circular DNA is characteristic of many species from the domain Archaea (23). Thus, several strains of halophilic archaea contain plasmids that range in size from 30 to 100 kbp and exist in a relatively low number of copies per cell (1, 4-6, 11, 18, 19). In addition, a small plasmid (about 1.7 kbp) with a high copy number has been found in three halobacterial isolates, SB3, GRB, and GN101 (5). The small plasmids from these three strains are closely related, as originally revealed by hybridization analysis (5) and later by sequencing (7-9, 14), but share no detectable homology either with the chromosome of the host strains or with DNAs of other halobacteria. The existence of a small amount of a single-stranded plasmid form in the cell may represent an intermediate generated by rolling-circle replication (22).While cloning and sequencing a small plasmid from the SB3 strain, we observed that some of the presumably identical recombinant plasmids isolated from the transformed Escherichia coli colonies in fact differed from each other by a few base changes (13). This unexpected phenomenon was examined in detail, and in this report we present evidence that the small plasmids in a halobacterial cell do not have a unique sequence but, instead, exist as a population of closely related sequences. Two main types of heterogeneity were detected: microheterogeneity, in which individual plasmids differ from each other by one or a few nucleotide substitutions, and macroheterogeneity, represented by two major plasmid versions exhibiting about 80% homology. MATERIALS AND METHODSStrains, media, and enzymes. Halobacterium strains SB3, GRB, and GN101 (5) All of the enzymes used in this work were from Biopreparat (Vilnius, Lithuania).Plasmid isolation and DNA analyses. Halobacterial colonies were isolated by a spreading technique (20), and cell cultures were grown from individual clones. Cells were harvested at the early stationary phase (A550, -1.2), and total plasmids were isolated from cultures by a conventional NaOH-sodium dodecyl sulfate procedure (20) with omission of lysozyme from the lysis buffer. RNA was removed by RNase treatment and polyethylene glycol precipitation (10), and the supercoi...

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“…pHH1 and a 36-kbp deletion derivative (pHH4) found in a pvac-negative mutant gave rise to further deletion variants. With pHH4 as the parental plasmid, deletion derivatives with sizes of 20 to 5.7 kbp occur at high frequency during development of a colony (13). The deletion plasmids can be visualized by using a defined DNA fragment that presumably contains the functions necessary for pHH1 replication as a probe in Southern analysis.…”

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confidence: 99%

Insertion elements and deletion formation in a halophilic archaebacterium

Pfeifer

Blaseio

1989

J Bacteriol

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Deletion events that occur spontaneously in 36-kilobase-pair (kbp) plasmid pHH4 from the archaebacterium Halobacterium halobium were investigated. Four different deletion derivatives with sizes ranging from 5.7 to 17 kbp were isolated. Three of these deletion variants derived from pHH4 (pHH6 [17 kbp], pHH7 [16 kbpJ, and pHH8 [6.3 kbpJ), whereas the 5.7-kbp plasmid pHH9 derived from pHH6. Strains containing pHH6, pHH7, or pHH9 each lacked the parental plasmid pHH4, while pHH8 occurred at a 1:1 ratio together with p4H4. Common to all of these plasmids was the 5.7-kbp region of pHH9 DNA. The regions containing the fusion site in the deletion derivatives were investigated and compared with the corresponding area of the parental plasmid. Each deletion occurred exactly at the terminus of an insertion element. In pHH6 and pHH7, a halobacterial insertion element (ISH2) was located at the deletion site. The DNA fused to ISH2 displayed a 7-base-pair (bp) (pHH7) or 10-bp (pHH6) sequence homology to the inverted repeat of ISH2. In the two smaller plasmids, pHH8 and pHH9, an ISH27 element was located at the deletion site. Most likely, all of these smaller plasmids resulted from an intramolecular transposition event. The ISH27 insertion sequence contains a 16-bp terminal inverted repeat and duplicates 5 bp of target DNA during the transposition with the specificity 5'ANNNT3'. Four ISH27 copies were analyzed, and two ISH27 element types were identified that have approximately 85% sequence similarity. The ISH27 insertion elements constitute a family which is related to the ISH51 family characterized for H. volcanii, another halophilic archaebacterium.

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Dynamic plasmid populations in Halobacterium halobium

Abstract: Deletion events occurring in the major 150-kilobase-pair (kb)

Cited by 28 publications

References 15 publications

Growth competition between Halobacterium salinarium strain PHH1 and mutants affected in gas vesicle synthesis

Growth competition between Halobacterium salinarium strain PHH1 and mutants affected in gas vesicle synthesis

Heterogeneity of small plasmids from halophilic archaea

Insertion elements and deletion formation in a halophilic archaebacterium

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