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Feng Y, Arsenault D, Louyakis AS, Altman-Price N, Gophna U, Papke RT, Gogarten JP. Using the pan-genomic framework for the discovery of genomic islands in the haloarchaeon Halorubrum ezzemoulense. mBio 2024; 15:e0040824. [PMID: 38619241 PMCID: PMC11078007 DOI: 10.1128/mbio.00408-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2024] [Accepted: 03/19/2024] [Indexed: 04/16/2024] Open
Abstract
In this study, we use pan-genomics to characterize the genomic variability of the widely dispersed halophilic archaeal species Halorubrum ezzemoulense (Hez). We include a multi-regional sampling of newly sequenced, high-quality draft genomes. The pan-genome graph of the species reveals 50 genomic islands that represent rare accessory genetic capabilities available to members. Most notably, we observe rearrangements that have led to the insertion/recombination/replacement of mutually exclusive genomic islands in equivalent genome positions ("homeocassettes"). These conflicting islands encode for similar functions, but homologs from islands located between the same core genes exhibit high divergence on the amino acid level, while the neighboring core genes are nearly identical. Both islands of a homeocassette often coexist in the same geographic location, suggesting that either island may be beyond the reach of selective sweeps and that these loci of divergence between Hez members are maintained and persist long term. This implies that subsections of the population have different niche preferences and rare metabolic capabilities. After an evaluation of the gene content in the homeocassettes, we speculate that these islands may play a role in the speciation, niche adaptability, and group selection dynamics in Hez. Though homeocassettes are first described in this study, similar replacements and divergence of genes on genomic islands have been previously reported in other Haloarchaea and distantly related Archaea, suggesting that homeocassettes may be a feature in a wide range of organisms outside of Hez.IMPORTANCEThis study catalogs the rare genes discovered in strains of the species Halorubrum ezzemoulense (Hez), an obligate halophilic archaeon, through the perspective of its pan-genome. These rare genes are often found to be arranged on islands that confer metabolic and transport functions and contain genes that have eluded previous studies. The discovery of divergent, but homologous islands occupying equivalent genome positions ("homeocassettes") in different genomes, reveals significant new information on genome evolution in Hez. Homeocassette pairs encode for similar functions, but their dissimilarity and distribution imply high rates of recombination, different specializations, and niche preferences in Hez. The coexistence of both islands of a homeocassette pair in multiple environments demonstrates that both islands are beyond the reach of selective sweeps and that these genome content differences between strains persist long term. The switch between islands through recombination under different environmental conditions may lead to a greater range of niche adaptability in Hez.
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Affiliation(s)
- Yutian Feng
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut, USA
| | - Danielle Arsenault
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut, USA
| | - Artemis S. Louyakis
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut, USA
| | - Neta Altman-Price
- The Shmunis School of Biomedicine and Cancer Research, Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
- Avinoam Adam Department of Natural Sciences, The Open University of Israel, Raanana, Israel
| | - Uri Gophna
- The Shmunis School of Biomedicine and Cancer Research, Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - R. Thane Papke
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut, USA
| | - Johann Peter Gogarten
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut, USA
- Institute for Systems Genomics, University of Connecticut, Storrs, Connecticut, USA
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Genomic analysis of heavy metal-resistant Halobacterium salinarum isolated from Sfax solar saltern sediments. Extremophiles 2022; 26:25. [PMID: 35842547 PMCID: PMC9288257 DOI: 10.1007/s00792-022-01273-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2022] [Accepted: 06/30/2022] [Indexed: 02/06/2023]
Abstract
The draft genome sequences of five archaeal strains, isolated from Sfax solar saltern sediments and affiliated with Halobacterium salinarum, were analyzed in order to reveal their adaptive strategies to live in hypersaline environments polluted with heavy metals. The genomes of the strains (named AS1, AS2, AS8, AS11, and AS19) are found to contain 2,060,688; 2,467,461; 2,236,624; 2,432,692; and 2,428,727 bp respectively, with a G + C content of 65.5, 66.0, 67.0, and 66.2%. The majority of these genes (43.69–55.65%) are annotated as hypothetical proteins. Growth under osmotic stress is possible by genes coding for potassium uptake, sodium efflux, and kinases, as well as stress proteins, DNA repair systems, and proteasomal components. These strains harbor many genes responsible for metal transport/resistance, such as: copper-translocating P-type ATPases, ABC transporter, and cobalt-zinc-cadmium resistance protein. In addition, detoxification enzymes and secondary metabolites are also identified. The results show strain AS1, as compared to the other strains, is more adapted to heavy metals and may be used in the bioremediation of multi-metal contaminated environments. This study highlights the presence of several commercially valuable bioproducts (carotenoids, retinal proteins, exopolysaccharide, stress proteins, squalene, and siderophores) and enzymes (protease, sulfatase, phosphatase, phosphoesterase, and chitinase) that can be used in many industrial applications.
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3
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Han HL, Danganan RE, Li Z, Shin NR, Bennett RM, Dedeles GR, Kim SG. Halorubrum salinarum sp. nov., an extremely halophilic archaeon isolated from a saturated brine pond of a saltern. Int J Syst Evol Microbiol 2022; 72. [DOI: 10.1099/ijsem.0.005231] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
A novel extremely halophilic archaeon, strain RHB-CT, was isolated from a saturated brine pond of a solar saltern in Bolinao, Pangasinan, Philippines. Colonies were orange-red-pigmented, smooth, convex and round on a solid modified growth medium containing 25 % (w/v) of total salts. Cells of strain RHB-CT on the solid modified growth medium were ovoid-shaped (0.89–2.66 µm long), while the cells in a liquid modified growth medium were rod-shaped (1.53–5.65 µm long and 0.45–1.03 µm wide). The strain was Gram-stain-negative, motile and strictly aerobic. Strain RHB-CT grew with NaCl concentrations ranging from 10 to 30 % (w/v; optimum, 20–25 %), at pH 6.5–8.5 (optimum, pH 7.0–7.5) and at 20–55 °C (optimum, 40–45 °C). Furthermore, the strain grew even in the absence of Mg2+; however, when supplemented with Mg2+, growth was observed optimally at 0.2–0.4 M Mg2+. The 16S rRNA gene phylogeny inferred that the strain is a member of the genus
Halorubrum
and was related to
Halorubrum xinjiangense
CGMCC 1.3527T (99.0 %),
Halorubrum sodomense
DSM 3755T (98.8 %),
Halorubrum coriense
Ch2T (98.8 %),
Halorubrum trapanicum
NRC 34021T (98.4 %) and
Halorubrum distributum
JCM 9100T (98.1 %). The rpoB′ gene sequences also showed that strain RHB-CT is related to Hrr. xinjiangense JCM 12388T (97.1 %), Hrr. distributum JCM 9100T (97.1 %), Hrr. coriense JCM 9275T (96.5 %), Hrr. californiense JCM 14715T (96.5 %), Hrr. trapanicum JCM 10477T (96.3%), Hrr. sodomense JCM 8880T (96.2%) and Hrr. tebenquichense DSM 14210T (95.6 %). The DNA G+C content of strain RHB-CT was 68.7 mol% (genome). Digital DNA–DNA hybridization (dDDH) and average nucleotide identity (ANI) values between strain RHB-CT and the closely related species of
Halorubrum
were below 40 and 90 %, respectively, which are far below the thresholds to delineate a new species. The polar lipids of strain RHB-CT were phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester, phosphatidylglycerol sulphate and sulfated mannosyl glycosyl diether. Based on dDDH and ANI values, and the significant morphological and physiological differences from known taxa, it is hereby suggested that strain RHB-CT represents a novel species of the genus
Halorubrum
, for which the name Halorubrum salinarum sp. nov. is proposed. The type strain is RHB-CT (=KCTC 4274T=CMS 2103T).
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Affiliation(s)
- Ho Le Han
- University of Science and Technology (UST), Yuseong, Daejeon 34113, Republic of Korea
- Biological Resource Center/Korean Collection for Type Cultures (KCTC), Korea Research Institute of Bioscience and Biotechnology, Jeongeup, Jeonbuk 56212, Republic of Korea
| | - Reneelyn E. Danganan
- Laboratory of Pure and Applied Microbiology, Research Center for the Natural and Applied Sciences, University of Santo Tomas, Manila, Philippines
- The Graduate School, University of Santo Tomas, Manila, Philippines
| | - Zhun Li
- Biological Resource Center/Korean Collection for Type Cultures (KCTC), Korea Research Institute of Bioscience and Biotechnology, Jeongeup, Jeonbuk 56212, Republic of Korea
| | - Na-Ri Shin
- Biological Resource Center/Korean Collection for Type Cultures (KCTC), Korea Research Institute of Bioscience and Biotechnology, Jeongeup, Jeonbuk 56212, Republic of Korea
| | - Reuel M. Bennett
- Department of Biological Sciences, College of Science, University of Santo Tomas, Manila, Philippines
| | - Gina R. Dedeles
- Laboratory of Pure and Applied Microbiology, Research Center for the Natural and Applied Sciences, University of Santo Tomas, Manila, Philippines
- Department of Biological Sciences, College of Science, University of Santo Tomas, Manila, Philippines
- Collection of Microbial Strains, University of Santo Tomas, Manila, Philippines
- The Graduate School, University of Santo Tomas, Manila, Philippines
| | - Song-Gun Kim
- Biological Resource Center/Korean Collection for Type Cultures (KCTC), Korea Research Institute of Bioscience and Biotechnology, Jeongeup, Jeonbuk 56212, Republic of Korea
- University of Science and Technology (UST), Yuseong, Daejeon 34113, Republic of Korea
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Wang X, Gao Y, Liu X, Sun N, Huang J, Wang L. First Report of the Plasmid-mediated fosB Gene in Enterococcus faecalis from Pigs. Genes (Basel) 2021; 12:genes12111684. [PMID: 34828290 PMCID: PMC8624268 DOI: 10.3390/genes12111684] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2021] [Revised: 10/13/2021] [Accepted: 10/21/2021] [Indexed: 11/16/2022] Open
Abstract
Plasmid-mediated fosfomycin determinants is a global public health concern due to the increasing dissemination of fosfomycin resistance and limited clinical treatment options. Information about the fosfomycin resistant and molecular genetic among Enterococcus spp. is still lacking. In this study, we found the first plasmid-medieted fosB in Enterococcus faecalis from pigs, and all the fosfomycin resistant Enterococcus spp. (FRE) isolates were multi-drug resistant. S1-PFGE, Southern blot and conjugation experiments indicated that the fosB gene located on ~54.7 kb transferable plasmids. Relative competition assay confirmed that the fosB-carrying plasmid impaired fitness in recipient E. faecalis JH2-2. Illumina and the MinION sequencing data revealed that both E. faecalis ES-1 and ES-2 isolates belonged to novel ST (ST964), and had 71 SNPs difference. WGS showed that the genetic environments of fosB were diverse among different species, and the linezolid resistance gene optrA was found in the fosB-carrying strains. To summarize, for the first time, we reported plasmid-mediated fosB in E. faecalis from pigs. And, the co-occurrence of fosB and optrA pose a serious threat to public health.
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Najjari A, Stathopoulou P, Elmnasri K, Hasnaoui F, Zidi I, Sghaier H, Ouzari HI, Cherif A, Tsiamis G. Assessment of 16S rRNA Gene-Based Phylogenetic Diversity of Archaeal Communities in Halite-Crystal Salts Processed from Natural Saharan Saline Systems of Southern Tunisia. BIOLOGY 2021; 10:biology10050397. [PMID: 34064384 PMCID: PMC8147861 DOI: 10.3390/biology10050397] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/04/2021] [Revised: 03/29/2021] [Accepted: 03/30/2021] [Indexed: 12/27/2022]
Abstract
A thorough assessment of the phylogenetic diversity and community structure of halophilic archaea from three halite-crystal salts, processed from two separated saline systems of Southern Tunisia has been performed using culture dependent and independent methods targeting different regions of 16S rRNA gene sequences including DGGE, 16S rRNA clone libraries and Illumina Miseq sequencing. Two samples, CDR (red halite-crystal salts) and CDW (white halite-crystal salts), were collected from Chott-Eljerid and one sample CDZ (white halite-crystal salts) from Chott Douz. Fourteen isolates were identified as Halorubrum, Haloferax, Haloarcula, and Halogeometricum genera members. Culture-independent approach revealed a high diversity of archaeal members present in all samples, represented by the Euryarchaeal phylum and the dominance of the Halobacteria class. Nanohaloarchaea were also identified only in white halite samples based on metagenomic analysis. In fact, a total of 61 genera were identified with members of the Halorhabdus, Halonotius, Halorubrum, Haloarcula, and unclassified. Halobacteriaceae were shared among all samples. Unexpected diversity profiles between samples was observed where the red halite crust sample was considered as the most diverse one. The highest diversity was observed with Miseq approach, nevertheless, some genera were detected only with 16S rRNA clone libraries and cultured approaches.
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Affiliation(s)
- Afef Najjari
- Faculté des Sciences de Tunis, LR03ES03 Laboratoire de Microbiologie et Biomolécules Actives, Université Tunis El Manar, 2092 Tunis, Tunisia; (F.H.); (I.Z.); (H.I.O.)
- Correspondence:
| | - Panagiota Stathopoulou
- Department of Environmental Engineering, Laboratory of Systems Microbiology and Applied Genomics, University of Patras, 2 Seferi Str., 30100 Agrinio, Greece; (P.S.); (G.T.)
| | - Khaled Elmnasri
- Higher Institute for Biotechnology, University Manouba, BVBGR-LR11ES31, Biotechpole Sidi Thabet, 2020 Ariana, Tunisia; (K.E.); (H.S.); (A.C.)
| | - Faten Hasnaoui
- Faculté des Sciences de Tunis, LR03ES03 Laboratoire de Microbiologie et Biomolécules Actives, Université Tunis El Manar, 2092 Tunis, Tunisia; (F.H.); (I.Z.); (H.I.O.)
| | - Ines Zidi
- Faculté des Sciences de Tunis, LR03ES03 Laboratoire de Microbiologie et Biomolécules Actives, Université Tunis El Manar, 2092 Tunis, Tunisia; (F.H.); (I.Z.); (H.I.O.)
| | - Haitham Sghaier
- Higher Institute for Biotechnology, University Manouba, BVBGR-LR11ES31, Biotechpole Sidi Thabet, 2020 Ariana, Tunisia; (K.E.); (H.S.); (A.C.)
- Laboratory “Energy and Matter for Development of Nuclear Sciences” (LR16CNSTN02), National Center for Nuclear Sciences and Technology (CNSTN), 2020 Sidi Thabet, Tunisia
| | - Hadda Imene Ouzari
- Faculté des Sciences de Tunis, LR03ES03 Laboratoire de Microbiologie et Biomolécules Actives, Université Tunis El Manar, 2092 Tunis, Tunisia; (F.H.); (I.Z.); (H.I.O.)
| | - Ameur Cherif
- Higher Institute for Biotechnology, University Manouba, BVBGR-LR11ES31, Biotechpole Sidi Thabet, 2020 Ariana, Tunisia; (K.E.); (H.S.); (A.C.)
| | - George Tsiamis
- Department of Environmental Engineering, Laboratory of Systems Microbiology and Applied Genomics, University of Patras, 2 Seferi Str., 30100 Agrinio, Greece; (P.S.); (G.T.)
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6
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Ramírez-Durán N, de la Haba RR, Vera-Gargallo B, Sánchez-Porro C, Alonso-Carmona S, Sandoval-Trujillo H, Ventosa A. Taxogenomic and Comparative Genomic Analysis of the Genus Saccharomonospora Focused on the Identification of Biosynthetic Clusters PKS and NRPS. Front Microbiol 2021; 12:603791. [PMID: 33776952 PMCID: PMC7990883 DOI: 10.3389/fmicb.2021.603791] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2020] [Accepted: 02/17/2021] [Indexed: 11/13/2022] Open
Abstract
Actinobacteria are prokaryotes with a large biotechnological interest due to their ability to produce secondary metabolites, produced by two main biosynthetic gene clusters (BGCs): polyketide synthase (PKS) and non-ribosomal peptide synthetase (NRPS). Most studies on bioactive products have been carried out on actinobacteria isolated from soil, freshwater or marine habitats, while very few have been focused on halophilic actinobacteria isolated from extreme environments. In this study we have carried out a comparative genomic analysis of the actinobacterial genus Saccharomonospora, which includes species isolated from soils, lake sediments, marine or hypersaline habitats. A total of 19 genome sequences of members of Saccharomonospora were retrieved and analyzed. We compared the 16S rRNA gene-based phylogeny of this genus with evolutionary relationships inferred using a phylogenomic approach obtaining almost identical topologies between both strategies. This method allowed us to unequivocally assign strains into species and to identify some taxonomic relationships that need to be revised. Our study supports a recent speciation event occurring between Saccharomonospora halophila and Saccharomonospora iraqiensis. Concerning the identification of BGCs, a total of 18 different types of BGCs were detected in the analyzed genomes of Saccharomonospora, including PKS, NRPS and hybrid clusters which might be able to synthetize 40 different putative products. In comparison to other genera of the Actinobacteria, members of the genus Saccharomonospora showed a high degree of novelty and diversity of BGCs.
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Affiliation(s)
- Ninfa Ramírez-Durán
- Faculty of Medicine, Autonomous University of the State of Mexico, Toluca, Mexico.,Department of Microbiology and Parasitology, Faculty of Pharmacy, University of Sevilla, Seville, Spain
| | - Rafael R de la Haba
- Department of Microbiology and Parasitology, Faculty of Pharmacy, University of Sevilla, Seville, Spain
| | - Blanca Vera-Gargallo
- Department of Microbiology and Parasitology, Faculty of Pharmacy, University of Sevilla, Seville, Spain
| | - Cristina Sánchez-Porro
- Department of Microbiology and Parasitology, Faculty of Pharmacy, University of Sevilla, Seville, Spain
| | | | - Horacio Sandoval-Trujillo
- Department of Biological Systems, Metropolitan Autonomous University-Xochimilco, Mexico City, Mexico
| | - Antonio Ventosa
- Department of Microbiology and Parasitology, Faculty of Pharmacy, University of Sevilla, Seville, Spain
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7
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Klempay B, Arandia-Gorostidi N, Dekas AE, Bartlett DH, Carr CE, Doran PT, Dutta A, Erazo N, Fisher LA, Glass JB, Pontefract A, Som SM, Wilson JM, Schmidt BE, Bowman JS. Microbial diversity and activity in Southern California salterns and bitterns: analogues for remnant ocean worlds. Environ Microbiol 2021; 23:3825-3839. [PMID: 33621409 DOI: 10.1111/1462-2920.15440] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Revised: 02/12/2021] [Accepted: 02/15/2021] [Indexed: 01/02/2023]
Abstract
Concurrent osmotic and chaotropic stress make MgCl2 -rich brines extremely inhospitable environments. Understanding the limits of life in these brines is essential to the search for extraterrestrial life on contemporary and relict ocean worlds, like Mars, which could host similar environments. We sequenced environmental 16S rRNA genes and quantified microbial activity across a broad range of salinity and chaotropicity at a Mars-analogue salt harvesting facility in Southern California, where seawater is evaporated in a series of ponds ranging from kosmotropic NaCl brines to highly chaotropic MgCl2 brines. Within NaCl brines, we observed a proliferation of specialized halophilic Euryarchaeota, which corresponded closely with the dominant taxa found in salterns around the world. These communities were characterized by very slow growth rates and high biomass accumulation. As salinity and chaotropicity increased, we found that the MgCl2 -rich brines eventually exceeded the limits of microbial activity. We found evidence that exogenous genetic material is preserved in these chaotropic brines, producing an unexpected increase in diversity in the presumably sterile MgCl2 -saturated brines. Because of their high potential for biomarker preservation, chaotropic brines could therefore serve as repositories of genetic biomarkers from nearby environments (both on Earth and beyond) making them prime targets for future life-detection missions.
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Affiliation(s)
- Benjamin Klempay
- Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA, 92037, USA
| | | | - Anne E Dekas
- Department of Earth System Science, Stanford University, Stanford, CA, 94305, USA
| | - Douglas H Bartlett
- Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA, 92037, USA
| | - Christopher E Carr
- Daniel Guggenheim School of Aerospace Engineering, Georgia Institute of Technology, Atlanta, GA, 30332, USA.,School of Earth and Atmospheric Studies, Georgia Institute of Technology, Atlanta, GA, 30332, USA
| | - Peter T Doran
- Department of Geology and Geophysics, Louisiana State University, Baton Rouge, LA, 70803, USA
| | - Avishek Dutta
- Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA, 92037, USA
| | - Natalia Erazo
- Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA, 92037, USA
| | - Luke A Fisher
- Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA, 92037, USA
| | - Jennifer B Glass
- School of Earth and Atmospheric Studies, Georgia Institute of Technology, Atlanta, GA, 30332, USA
| | | | - Sanjoy M Som
- Blue Marble Space Institute of Science, Seattle, WA, 98154, USA
| | - Jesse M Wilson
- Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA, 92037, USA
| | - Britney E Schmidt
- School of Earth and Atmospheric Studies, Georgia Institute of Technology, Atlanta, GA, 30332, USA
| | - Jeff S Bowman
- Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA, 92037, USA
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Verma DK, Vasudeva G, Sidhu C, Pinnaka AK, Prasad SE, Thakur KG. Biochemical and Taxonomic Characterization of Novel Haloarchaeal Strains and Purification of the Recombinant Halotolerant α-Amylase Discovered in the Isolate. Front Microbiol 2020; 11:2082. [PMID: 32983058 PMCID: PMC7490331 DOI: 10.3389/fmicb.2020.02082] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2020] [Accepted: 08/07/2020] [Indexed: 11/13/2022] Open
Abstract
Haloarchaea are salt-loving archaea and potential source of industrially relevant halotolerant enzymes. In the present study, three reddish-pink, extremely halophilic archaeal strains, namely wsp1 (wsp-water sample Pondicherry), wsp3, and wsp4, were isolated from the Indian Solar saltern. The phylogenetic analysis based on 16S rRNA gene sequences suggests that both wsp3 and wsp4 strains belong to Halogeometricum borinquense while wsp1 is closely related to Haloferax volcanii species. The comparative genomics revealed an open pangenome for both genera investigated here. Whole-genome sequence analysis revealed that these isolates have multiple copies of industrially/biotechnologically important unique genes and enzymes. Among these unique enzymes, for recombinant expression and purification, we selected four putative α-amylases identified in these three isolates. We successfully purified functional halotolerant recombinant Amy2, from wsp1 using pelB signal sequence-based secretion strategy using Escherichia coli as an expression host. This method may prove useful to produce functional haloarchaeal secretory recombinant proteins suitable for commercial or research applications. Biochemical analysis of Amy2 suggests the halotolerant nature of the enzyme having maximum enzymatic activity observed at 1 M NaCl. We also report the isolation and characterization of carotenoids purified from these isolates. This study highlights the presence of several industrially important enzymes in the haloarchaeal strains which may potentially have improved features like stability and salt tolerance suitable for industrial applications.
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Affiliation(s)
- Dipesh Kumar Verma
- G. N. Ramachandran Protein Centre, Structural Biology Laboratory, Council of Scientific and Industrial Research-Institute of Microbial Technology, Chandigarh, India
| | - Gunjan Vasudeva
- MTCC-Microbial Type Culture Collection and Gene Bank, CSIR-Institute of Microbial Technology, Chandigarh, India
| | - Chandni Sidhu
- MTCC-Microbial Type Culture Collection and Gene Bank, CSIR-Institute of Microbial Technology, Chandigarh, India
| | - Anil K Pinnaka
- MTCC-Microbial Type Culture Collection and Gene Bank, CSIR-Institute of Microbial Technology, Chandigarh, India
| | - Senthil E Prasad
- Biochemical Engineering Research and Process Development Centre, Council of Scientific and Industrial Research-Institute of Microbial Technology, Chandigarh, India
| | - Krishan Gopal Thakur
- G. N. Ramachandran Protein Centre, Structural Biology Laboratory, Council of Scientific and Industrial Research-Institute of Microbial Technology, Chandigarh, India
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9
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Testing the “(Neo-)Darwinian” Principles against Reticulate Evolution: How Variation, Adaptation, Heredity and Fitness, Constraints and Affordances, Speciation, and Extinction Surpass Organisms and Species. INFORMATION 2020. [DOI: 10.3390/info11070352] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Variation, adaptation, heredity and fitness, constraints and affordances, speciation, and extinction form the building blocks of the (Neo-)Darwinian research program, and several of these have been called “Darwinian principles”. Here, we suggest that caution should be taken in calling these principles Darwinian because of the important role played by reticulate evolutionary mechanisms and processes in also bringing about these phenomena. Reticulate mechanisms and processes include symbiosis, symbiogenesis, lateral gene transfer, infective heredity mediated by genetic and organismal mobility, and hybridization. Because the “Darwinian principles” are brought about by both vertical and reticulate evolutionary mechanisms and processes, they should be understood as foundational for a more pluralistic theory of evolution, one that surpasses the classic scope of the Modern and the Neo-Darwinian Synthesis. Reticulate evolution moreover demonstrates that what conventional (Neo-)Darwinian theories treat as intra-species features of evolution frequently involve reticulate interactions between organisms from very different taxonomic categories. Variation, adaptation, heredity and fitness, constraints and affordances, speciation, and extinction therefore cannot be understood as “traits” or “properties” of genes, organisms, species, or ecosystems because the phenomena are irreducible to specific units and levels of an evolutionary hierarchy. Instead, these general principles of evolution need to be understood as common goods that come about through interactions between different units and levels of evolutionary hierarchies, and they are exherent rather than inherent properties of individuals.
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10
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Infante-Domínguez C, de la Haba RR, Corral P, Sanchez-Porro C, Arahal DR, Ventosa A. Genome-based analyses reveal a synonymy among Halorubrum distributum Zvyagintseva and Tarasov 1989; Oren and Ventosa 1996, Halorubrum terrestre Ventosa et al. 2004, Halorubrum arcis Xu et al. 2007 and Halorubrum litoreum Cui et al. 2007. Emended description of Halorubrum distributum Zvyagintseva and Tarasov 1989; Oren and Ventosa 1996. Int J Syst Evol Microbiol 2020; 70:1698-1705. [PMID: 31971502 PMCID: PMC7386789 DOI: 10.1099/ijsem.0.003956] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
A comparative taxonomic study of Halorubrum distributum, Halorubrum terrestre, Halorubrum arcis and Halorubrum litoreum was carried out using different approaches, 16S rRNA gene sequence analysis, multilocus sequence analysis (MLSA), phylogenomic analysis based on the comparison of the core genome, orthologous average nucleotide identity (OrthoANI), Genome-to-Genome Distance Calculator (GGDC), synteny plots and polar lipid profile (PLP). The MLSA study, using the five concatenated housekeeping genes atpB, EF-2, glnA, ppsA and rpoB′, and the phylogenomic analysis based on 1347 core translated gene sequences obtained from their genomes showed that Halorubrum distributum JCM 9100T, Halorubrum terrestre JCM 10247T, Halorubrum arcis JCM 13916T and Halorubrum litoreum JCM 13561T formed a robust cluster, clearly separated from the rest of species of the genus Halorubrum. The OrthoANI and digital DDH values, calculated by the GGDC, showed percentages among Hrr. distributum JCM 9100T, Hrr. terrestre JCM 10247T, Hrr. arcis JCM 13916T and Hrr. litoreum JCM 13561T that ranged from 98.1 to 97.5 %, and 84.0 to 78.0 %, respectively, while these values among those strains and the type strains of their most related species of Halorubrum were equal or lower than 90.8 and 41.2 %, respectively. Moreover, degree of synteny across the four genomes was very high, especially between the genomes of Halorubrum litoreum JCM 13561T and Halorubrum arcis JCM 13916T. In addition, the PLP is quite similar among the four strains studied, showing a common pattern typical of the neutrophilic species of the genus Halorubrum. Overall, these data show that Hrr. distributum, Hrr. terrestre, Hrr. arcis and Hrr. litoreum constitute a single species. Thus, the latter three should be considered as later, heterotypic synonyms of Hrr. distributum based on the rules for priority of names. We propose an emended description of Hrr. distributum, including the features of Hrr. terrestre, Hrr. arcis and Hrr. litoreum.
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Affiliation(s)
- Carmen Infante-Domínguez
- Department of Microbiology and Parasitology, Faculty of Pharmacy, University of Sevilla, 41012 Sevilla, Spain
| | - Rafael R de la Haba
- Department of Microbiology and Parasitology, Faculty of Pharmacy, University of Sevilla, 41012 Sevilla, Spain
| | - Paulina Corral
- Department of Microbiology and Parasitology, Faculty of Pharmacy, University of Sevilla, 41012 Sevilla, Spain
| | - Cristina Sanchez-Porro
- Department of Microbiology and Parasitology, Faculty of Pharmacy, University of Sevilla, 41012 Sevilla, Spain
| | - David R Arahal
- Department of Microbiology and Ecology, and Spanish Type Culture Collection (CECT), University of Valencia, 46980 Paterna (Valencia), Spain
| | - Antonio Ventosa
- Department of Microbiology and Parasitology, Faculty of Pharmacy, University of Sevilla, 41012 Sevilla, Spain
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11
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Chen S, Sun S, Korfanty GA, Liu J, Xiang H. A Halocin Promotes DNA Uptake in Haloferax mediterranei. Front Microbiol 2019; 10:1960. [PMID: 31620096 PMCID: PMC6759562 DOI: 10.3389/fmicb.2019.01960] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2019] [Accepted: 08/09/2019] [Indexed: 11/13/2022] Open
Abstract
Halocins are antimicrobial peptides or proteins that are produced by halophilic archaea. Although their function in inhibiting the growth of closely related haloarchaeal strains is well known, other physiological functions of halocins have also been proposed in recent years. To unveil the possible function and mechanism of halocins in DNA uptake, the halocin H4 producing strain Haloferax mediterranei DF50-ΔEPS (incapable of EPS production) was used in this study. We found that deletion of the halH4 resulted in the strain DF50-ΔEPSΔhalH4 which exhibited loss of natural DNA uptake ability. Moreover, supernatants of the halocin producing strain were capable of inducing the ability to uptake DNA. Obviously, halocin is likely responsible for inducing DNA uptake. Cell surface ultrastructures of these strains are varied from strains DF50-ΔEPS to DF50-ΔEPSΔhalH4. The cell surface of strain DF50-ΔEPS is rough due to numerous pinholes, while that of the strain DF50-ΔEPSΔhalH4 is smooth without visible pinholes. The morphology of the halH4 complemented strain, DF50-ΔEPSΔhalH4::H4, shows an intermediate phenotype between strains DF50-ΔEPS and DF50-ΔEPSΔhalH4. We speculate that halocin H4 may accelerate DNA uptake by perforating the cell surface ultrastructure. The halocin H4 may represent a novel inducer or activator of DNA uptake in Hfx. mediterranei.
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Affiliation(s)
- Shaoxing Chen
- Anhui Provincial Key Laboratory of the Conservation and Exploitation of Biological Resources, College of Life Sciences, Anhui Normal University, Wuhu, China
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
| | - Siqi Sun
- Anhui Provincial Key Laboratory of the Conservation and Exploitation of Biological Resources, College of Life Sciences, Anhui Normal University, Wuhu, China
| | | | - Jingwen Liu
- Anhui Provincial Key Laboratory of the Conservation and Exploitation of Biological Resources, College of Life Sciences, Anhui Normal University, Wuhu, China
| | - Hua Xiang
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
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12
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Polyploidy in halophilic archaea: regulation, evolutionary advantages, and gene conversion. Biochem Soc Trans 2019; 47:933-944. [PMID: 31189733 DOI: 10.1042/bst20190256] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Revised: 05/10/2019] [Accepted: 05/13/2019] [Indexed: 12/20/2022]
Abstract
All analyzed haloarachea are polyploid. In addition, haloarchaea contain more than one type of chromosome, and thus the gene dosage can be regulated independently on different replicons. Haloarchaea and several additional archaea have more than one replication origin on their major chromosome, in stark contrast with bacteria, which have a single replication origin. Two of these replication origins of Haloferax volcanii have been studied in detail and turned out to have very different properties. The chromosome copy number appears to be regulated in response to growth phases and environmental factors. Archaea typically contain about two Origin Recognition Complex (ORC) proteins, which are homologous to eukaryotic ORC proteins. However, haloarchaea are the only archaeal group that contains a multitude of ORC proteins. All 16 ORC protein paralogs from H. volcanii are involved in chromosome copy number regulation. Polyploidy has many evolutionary advantages for haloarchaea, e.g. a high resistance to desiccation, survival over geological times, and the relaxation of cell cycle-specific replication control. A further advantage is the ability to grow in the absence of external phosphate while using the many genome copies as internal phosphate storage polymers. Very efficient gene conversion operates in haloarchaea and results in the unification of genome copies. Taken together, haloarchaea are excellent models to study many aspects of genome biology in prokaryotes, exhibiting properties that have not been found in bacteria.
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13
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Pestov NB, Kalinovsky DV, Larionova TD, Zakirova AZ, Modyanov NN, Okkelman IA, Korneenko TV. Properties of a cryptic lysyl oxidase from haloarchaeon Haloterrigena turkmenica. PeerJ 2019; 7:e6691. [PMID: 30984480 PMCID: PMC6452851 DOI: 10.7717/peerj.6691] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2018] [Accepted: 02/26/2019] [Indexed: 11/20/2022] Open
Abstract
Background Lysyl oxidases (LOX) have been extensively studied in mammals, whereas properties and functions of recently found homologues in prokaryotic genomes remain enigmatic. Methods LOX open reading frame was cloned from Haloterrigena turkmenica in an E. coli expression vector. Recombinant Haloterrigena turkmenica lysyl oxidase (HTU-LOX) proteins were purified using metal affinity chromatography under denaturing conditions followed by refolding. Amine oxidase activity has been measured fluorometrically as hydrogen peroxide release coupled with the oxidation of 10-acetyl-3,7-dihydroxyphenoxazine in the presence of horseradish peroxidase. Rabbit polyclonal antibodies were obtained and used in western blotting. Results Cultured H. turkmenica has no detectable amine oxidase activity. HTU-LOX may be expressed in E. coli with a high protein yield. The full-length protein gives no catalytic activity. For this reason, we hypothesized that the hydrophobic N-terminal region may interfere with proper folding and its removal may be beneficial. Indeed, truncated His-tagged HTU-LOX lacking the N-terminal hydrophobic signal peptide purified under denaturing conditions can be successfully refolded into an active enzyme, and a larger N-terminal truncation further increases the amine oxidase activity. Refolding is optimal in the presence of Cu2+ at pH 6.2 and is not sensitive to salt. HTU-LOX is sensitive to LOX inhibitor 3-aminopropionitrile. HTU-LOX deaminates usual substrates of mammalian LOX such as lysine-containing polypeptides and polymers. The major difference between HTU-LOX and mammalian LOX is a relaxed substrate specificity of the former. HTU-LOX readily oxidizes various primary amines including such compounds as taurine and glycine, benzylamine being a poor substrate. Of note, HTU-LOX is also active towards several aminoglycoside antibiotics and polymyxin. Western blotting indicates that epitopes for the anti-HTU-LOX polyclonal antibodies coincide with a high molecular weight protein in H. turkmenica cells. Conclusion H. turkmenica contains a lysyl oxidase gene that was heterologously expressed yielding an active recombinant enzyme with important biochemical features conserved between all known LOXes, for example, the sensitivity to 3-aminopropionitrile. However, the native function in the host appears to be cryptic. Significance This is the first report on some properties of a lysyl oxidase from Archaea and an interesting example of evolution of enzymatic properties after hypothetical horizontal transfers between distant taxa.
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Affiliation(s)
- Nikolay B Pestov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Moscow, Russia
| | | | | | - Alia Z Zakirova
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Moscow, Russia
| | - Nikolai N Modyanov
- Department of Physiology and Pharmacology, University of Toledo, Toledo, OH, United States of America
| | - Irina A Okkelman
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Moscow, Russia
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14
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Spang A, Offre P. Towards a systematic understanding of differences between archaeal and bacterial diversity. ENVIRONMENTAL MICROBIOLOGY REPORTS 2019; 11:9-12. [PMID: 30394664 PMCID: PMC7379672 DOI: 10.1111/1758-2229.12701] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/01/2018] [Revised: 06/12/2018] [Accepted: 10/02/2018] [Indexed: 06/08/2023]
Abstract
In this crystal ball, we discuss emerging methodologies that can help reaching a synthesis on the biodiversity of Archaea and Bacteria and thereby inform a central enigma in microbiology, i.e. the fundamental split between these primary domains of life and the apparent lower diversity of the Archaea.
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Affiliation(s)
- Anja Spang
- NIOZ, Royal Netherlands Institute for Sea Research, Department of Marine Microbiology and Biogeochemistryand Utrecht UniversityNL‐1790 ABDen BurgThe Netherlands
- Department of Cell and Molecular Biology, Science for Life LaboratoryUppsala UniversitySE‐75123UppsalaSweden
| | - Pierre Offre
- NIOZ, Royal Netherlands Institute for Sea Research, Department of Marine Microbiology and Biogeochemistryand Utrecht UniversityNL‐1790 ABDen BurgThe Netherlands
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15
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Kean KM, Karplus PA. Structure and role for active site lid of lactate monooxygenase from Mycobacterium smegmatis. Protein Sci 2018; 28:135-149. [PMID: 30207005 DOI: 10.1002/pro.3506] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2018] [Revised: 08/30/2018] [Accepted: 09/05/2018] [Indexed: 12/17/2022]
Abstract
Lactate monooxygenase (LMO) catalyzes the FMN-dependent "coupled" oxidation of lactate and O2 to acetate, carbon dioxide, and water, involving pyruvate and hydrogen peroxide as enzyme-bound intermediates. Other α-hydroxy acid oxidase family members follow an "uncoupled pathway," wherein the α-keto acid product quickly dissociates before the reduced flavin reacts with oxygen. Here, we report the structures of Mycobacterium smegmatis wild-type LMO and a wild-type-like C203A variant at 2.1 Å and 1.7 Å resolution, respectively. The overall LMO fold and active site organization, including a bound sulfate mimicking substrate, resemble those of other α-hydroxy acid oxidases. Based on structural similarity, LMO is similarly distant from lactate oxidase, glycolate oxidase, mandelate dehydrogenase, and flavocytochrome b2 and is the first representative enzyme of its type. Comparisons with other α-hydroxy acid oxidases reveal that LMO has a longer and more compact folded active site loop (Loop 4), which is known in related flavoenzymes to undergo order/disorder transitions to allow substrate/product binding and release. We propose that LMO's Loop 4 has an enhanced stability that is responsible for the slow product release requisite for the coupled pathway. We also note electrostatic features of the LMO active site that promote substrate binding. Whereas the physiological role of LMO remains unknown, we document what can currently be assessed of LMO's distribution in nature, including its unexpected occurrence, presumably through horizontal gene transfer, in halophilic archaea and in a limited group of fungi of the genus Beauveria. BROAD STATEMENT OF IMPACT: This first crystal structure of the FMN-dependent α-hydroxy acid oxidase family member lactate monooxygenase (LMO) reveals it has a uniquely large active site lid that we hypothesize is stable enough to explain the slow dissociation of pyruvate that leads to its "coupled" oxidation of lactate and O2 to produce acetate, carbon dioxide, and water. Also, the relatively widespread distribution of putative LMOs supports their importance and provides new motivation for their further study.
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Affiliation(s)
- Kelsey M Kean
- Department of Biochemistry and Biophysics, 2011 Agriculture and Life Sciences Building, Oregon State University, Corvallis, Oregon 97331
| | - P Andrew Karplus
- Department of Biochemistry and Biophysics, 2011 Agriculture and Life Sciences Building, Oregon State University, Corvallis, Oregon 97331
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16
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Abstract
All organisms must adapt to ever-changing environmental conditions and accordingly have evolved diverse signal transduction systems. In bacteria, the most abundant networks are built around the two-component signal transduction systems that include histidine kinases and receiver domains. In contrast, eukaryotic signal transduction is dominated by serine/threonine/tyrosine protein kinases. Both of these systems are also found in archaea, but they are not as common and diversified as their bacterial and eukaryotic counterparts, suggesting the possibility that archaea have evolved other, still uncharacterized signal transduction networks. Here we propose a role for KaiC family ATPases, known to be key components of the circadian clock in cyanobacteria, in archaeal signal transduction. The KaiC family is notably expanded in most archaeal genomes, and although most of these ATPases remain poorly characterized, members of the KaiC family have been shown to control archaellum assembly and have been found to be a stable component of the gas vesicle system in Halobacteria Computational analyses described here suggest that KaiC-like ATPases and their homologues with inactivated ATPase domains are involved in many other archaeal signal transduction pathways and comprise major hubs of complex regulatory networks. We predict numerous input and output domains that are linked to KaiC-like proteins, including putative homologues of eukaryotic DEATH domains that could function as adapters in archaeal signaling networks. We further address the relationships of the archaeal family of KaiC homologues to the bona fide KaiC of cyanobacteria and implications for the existence of a KaiC-based circadian clock apparatus in archaea.IMPORTANCE Little is currently known about signal transduction pathways in Archaea Recent studies indicate that KaiC-like ATPases, known as key components of the circadian clock apparatus in cyanobacteria, are involved in the regulation of archaellum assembly and, likely, type IV pili and the gas vesicle system in Archaea We performed comprehensive comparative genomic analyses of the KaiC family. A vast protein interaction network was revealed, with KaiC family proteins as hubs for numerous input and output components, many of which are shared with two-component signal transduction systems. Putative KaiC-based signal transduction systems are predicted to regulate the activities of membrane-associated complexes and individual proteins, such as signal recognition particle and membrane transporters, and also could be important for oxidative stress response regulation. KaiC-centered signal transduction networks are predicted to play major roles in archaeal physiology, and this work is expected to stimulate their experimental characterization.
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17
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Halorubrum salsamenti sp. nov., a Novel Halophilic Archaeon Isolated from a Brine of Salt Mine. Curr Microbiol 2017; 74:1358-1364. [PMID: 28819743 DOI: 10.1007/s00284-017-1325-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2017] [Accepted: 08/02/2017] [Indexed: 01/06/2023]
Abstract
A non-motile, spherical or oval extremely halophilic archaeon, strain Y69T, was isolated from a brine of the Yunnan salt mine, China. Colonies on JCM 168 agar plate were round (1-2 mm in diameter), moist, and orange-pigmented. Phylogenetic analysis of the almost-complete 16S rRNA gene sequence showed that the isolate belonged to the species of the genus Halorubrum, with a close relationship to Halorubrum aidingense 31-hongT (98.5%), Halorubrum lacusprofundi ATCC 49239T (98.2%), and Halorubrum kocurii BG-1T (98.0%). The major polar lipids of strain Y69T were phosphatidylglycerol phosphate methyl ester, phosphatidylglycerol sulfate and a sulfated diglycosyl diether. Strain Y69T grew in 15-30% (w/v) NaCl. The temperature and pH ranges for growth were 25-50 °C and 6.5-9.0, respectively. Optimal growth occurred at 20% (w/v) NaCl, 42 °C, and pH 8.0. Mg2+ was required for growth. The DNA G+C content was determined to be 65.1 mol% by the thermal denaturation method. DNA-DNA hybridization values between strain Y69T and the closely related species were lower than 70%. Based on the data presented in this study, strain Y69T represents a novel species for which the name Halorubrum salsamenti sp. nov. is proposed. The type of the strain is Y69T (=CGMCC 1.15455T = JCM 31270T).
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Booth A, Mariscal C, Doolittle WF. The Modern Synthesis in the Light of Microbial Genomics. Annu Rev Microbiol 2016; 70:279-97. [DOI: 10.1146/annurev-micro-102215-095456] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Austin Booth
- Department of Philosophy, Dalhousie University, Halifax B3H 4R2, Nova Scotia, Canada
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax B3H 4R2, Nova Scotia, Canada;
| | - Carlos Mariscal
- Department of Philosophy, Dalhousie University, Halifax B3H 4R2, Nova Scotia, Canada
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax B3H 4R2, Nova Scotia, Canada;
- Department of Philosophy, University of Nevada, Reno, Nevada 89557
| | - W. Ford Doolittle
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax B3H 4R2, Nova Scotia, Canada;
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Kotnik T, Weaver JC. Abiotic Gene Transfer: Rare or Rampant? J Membr Biol 2016; 249:623-631. [PMID: 27067073 DOI: 10.1007/s00232-016-9897-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2016] [Accepted: 04/05/2016] [Indexed: 11/25/2022]
Abstract
Phylogenetic studies reveal that horizontal gene transfer (HGT) plays a prominent role in evolution and genetic variability of life. Five biotic mechanisms of HGT among prokaryotic organisms have been extensively characterized: conjugation, competence, transduction, gene transfer agent particles, and transitory fusion with recombination, but it is not known whether they can account for all natural HGT. It is even less clear how HGT could have occurred before any of these mechanisms had developed. Here, we consider contemporary conditions and experiments on microorganisms to estimate possible roles of abiotic HGT-currently and throughout evolution. Candidate mechanisms include freeze-and-thaw, microbeads-agitation, and electroporation-based transformation, and we posit that these laboratory techniques have analogues in nature acting as mechanisms of abiotic HGT: freeze-and-thaw cycles in polar waters, agitation by sand at foreshores and riverbeds, and lightning-triggered electroporation in near-surface aqueous habitats. We derive conservative order-of-magnitude estimates for rates of microorganisms subjected to freeze-and-thaw cycles, sand agitation, and lightning-triggered electroporation, at 1024, 1019, and 1017 per year, respectively. Considering the yield of viable transformants, which is by far the highest in electroporation, we argue this may still favor lightning-triggered transformation over the other two mechanisms. Electroporation-based gene transfer also appears to be the most general of these abiotic candidates, and perhaps even of all known HGT mechanisms. Future studies should provide improved estimates of gene transfer rates and cell viability, currently and in the past, but to assess the importance of abiotic HGT in nature will likely require substantial progress-also in knowledge of biotic HGT.
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Affiliation(s)
- Tadej Kotnik
- Department of Biomedical Engineering, Faculty of Electrical Engineering, University of Ljubljana, Ljubljana, Slovenia.
| | - James C Weaver
- Harvard-MIT Division of Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, MA, USA
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