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Schultz J, Modolon F, Peixoto RS, Rosado AS. Shedding light on the composition of extreme microbial dark matter: alternative approaches for culturing extremophiles. Front Microbiol 2023; 14:1167718. [PMID: 37333658 PMCID: PMC10272570 DOI: 10.3389/fmicb.2023.1167718] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2023] [Accepted: 05/09/2023] [Indexed: 06/20/2023] Open
Abstract
More than 20,000 species of prokaryotes (less than 1% of the estimated number of Earth's microbial species) have been described thus far. However, the vast majority of microbes that inhabit extreme environments remain uncultured and this group is termed "microbial dark matter." Little is known regarding the ecological functions and biotechnological potential of these underexplored extremophiles, thus representing a vast untapped and uncharacterized biological resource. Advances in microbial cultivation approaches are key for a detailed and comprehensive characterization of the roles of these microbes in shaping the environment and, ultimately, for their biotechnological exploitation, such as for extremophile-derived bioproducts (extremozymes, secondary metabolites, CRISPR Cas systems, and pigments, among others), astrobiology, and space exploration. Additional efforts to enhance culturable diversity are required due to the challenges imposed by extreme culturing and plating conditions. In this review, we summarize methods and technologies used to recover the microbial diversity of extreme environments, while discussing the advantages and disadvantages associated with each of these approaches. Additionally, this review describes alternative culturing strategies to retrieve novel taxa with their unknown genes, metabolisms, and ecological roles, with the ultimate goal of increasing the yields of more efficient bio-based products. This review thus summarizes the strategies used to unveil the hidden diversity of the microbiome of extreme environments and discusses the directions for future studies of microbial dark matter and its potential applications in biotechnology and astrobiology.
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Affiliation(s)
- Júnia Schultz
- Red Sea Research Center, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia
- Computational Bioscience Research Center, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia
| | - Flúvio Modolon
- Red Sea Research Center, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia
- Laboratory of Molecular Microbial Ecology, Institute of Microbiology, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
| | - Raquel Silva Peixoto
- Red Sea Research Center, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia
- Computational Bioscience Research Center, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia
| | - Alexandre Soares Rosado
- Red Sea Research Center, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia
- Computational Bioscience Research Center, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia
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Khelaifia S, Virginie P, Belkacemi S, Tassery H, Terrer E, Aboudharam G. Culturing the Human Oral Microbiota, Updating Methodologies and Cultivation Techniques. Microorganisms 2023; 11:microorganisms11040836. [PMID: 37110259 PMCID: PMC10143722 DOI: 10.3390/microorganisms11040836] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2023] [Revised: 03/16/2023] [Accepted: 03/23/2023] [Indexed: 04/29/2023] Open
Abstract
Recent years have been marked by a paradigm shift in the study of the human microbiota, with a re-emergence of culture-dependent approaches. Numerous studies have been devoted to the human microbiota, while studies on the oral microbiota still remain limited. Indeed, various techniques described in the literature may enable an exhaustive study of the microbial composition of a complex ecosystem. In this article, we report different methodologies and culture media described in the literature that can be applied to study the oral microbiota by culture. We report on specific methodologies for targeted culture and specific culture techniques and selection methodologies for cultivating members of the three kingdoms of life commonly found in the human oral cavity, namely, eukaryota, bacteria and archaea. This bibliographic review aims to bring together the various techniques described in the literature, enabling a comprehensive study of the oral microbiota in order to demonstrate its involvement in oral health and diseases.
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Affiliation(s)
- Saber Khelaifia
- Institut Hospitalo-Universitaire Méditerranée-Infection, Aix-Marseille Univ, IRD, MEPHI, AP-HM, 19-21 Boulevard Jean Moulin, 13385 Marseille CEDEX 05, France
- Ecole de Médecine Dentaire, 27 Boulevard Jean Moulin, 13385 Marseille CEDEX 05, France
| | - Pilliol Virginie
- Institut Hospitalo-Universitaire Méditerranée-Infection, Aix-Marseille Univ, IRD, MEPHI, AP-HM, 19-21 Boulevard Jean Moulin, 13385 Marseille CEDEX 05, France
- Ecole de Médecine Dentaire, 27 Boulevard Jean Moulin, 13385 Marseille CEDEX 05, France
| | - Souad Belkacemi
- Institut Hospitalo-Universitaire Méditerranée-Infection, Aix-Marseille Univ, IRD, MEPHI, AP-HM, 19-21 Boulevard Jean Moulin, 13385 Marseille CEDEX 05, France
| | - Herve Tassery
- Ecole de Médecine Dentaire, 27 Boulevard Jean Moulin, 13385 Marseille CEDEX 05, France
| | - Elodie Terrer
- Institut Hospitalo-Universitaire Méditerranée-Infection, Aix-Marseille Univ, IRD, MEPHI, AP-HM, 19-21 Boulevard Jean Moulin, 13385 Marseille CEDEX 05, France
- Ecole de Médecine Dentaire, 27 Boulevard Jean Moulin, 13385 Marseille CEDEX 05, France
| | - Gérard Aboudharam
- Institut Hospitalo-Universitaire Méditerranée-Infection, Aix-Marseille Univ, IRD, MEPHI, AP-HM, 19-21 Boulevard Jean Moulin, 13385 Marseille CEDEX 05, France
- Ecole de Médecine Dentaire, 27 Boulevard Jean Moulin, 13385 Marseille CEDEX 05, France
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New Beta-lactamases in Candidate Phyla Radiation: Owning Pleiotropic Enzymes Is a Smart Paradigm for Microorganisms with a Reduced Genome. Int J Mol Sci 2022; 23:ijms23105446. [PMID: 35628255 PMCID: PMC9145738 DOI: 10.3390/ijms23105446] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2022] [Revised: 05/09/2022] [Accepted: 05/10/2022] [Indexed: 01/08/2023] Open
Abstract
The increased exploitation of microbial sequencing methods has shed light on the high diversity of new microorganisms named Candidate Phyla Radiation (CPR). CPR are mainly detected via 16S rRNA/metabarcoding analyses or metagenomics and are found to be abundant in all environments and present in different human microbiomes. These microbes, characterized by their symbiotic/epiparasitic lifestyle with bacteria, are directly exposed to competition with other microorganisms sharing the same ecological niche. Recently, a rich repertoire of enzymes with antibiotic resistance activity has been found in CPR genomes by using an in silico adapted screening strategy. This reservoir has shown a high prevalence of putative beta-lactamase-encoding genes. We expressed and purified five putative beta-lactamase sequences having the essential domains and functional motifs from class A and class B beta-lactamase. Their enzymatic activities were tested against various beta-lactam substrates using liquid chromatography-mass spectrometry (LC-MS) and showed some beta-lactamase activity even in the presence of a beta-lactamase inhibitor. In addition, ribonuclease activity was demonstrated against RNA that was not inhibited by sulbactam and EDTA. None of these proteins could degrade single- and double-stranded-DNA. This study is the first to express and test putative CPR beta-lactamase protein sequences in vitro. Our findings highlight that the reduced genomes of CPR members harbor sequences encoding for beta-lactamases known to be multifunction hydrolase enzymes.
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