Melhem Bilen

Culture of previously uncultured members of the human gut microbiota by culturomics

Metagenomics revolutionized the understanding of the relations among the human microbiome, health and diseases, but generated a countless number of sequences that have not been assigned to a known microorganism1. The pure culture of prokaryotes, neglected in recent decades, remains essential to elucidating the role of these organisms2. We recently introduced microbial culturomics, a culturing approach that uses multiple culture conditions and matrix-assisted laser desorption/ionization–time of flight and 16S rRNA for identification2. Here, we have selected the best culture conditions to increase the number of studied samples and have applied new protocols (fresh-sample inoculation; detection of microcolonies and specific cultures of Proteobacteria and microaerophilic and halophilic prokaryotes) to address the weaknesses of the previous studies3–5. We identified 1,057 prokaryotic species, thereby adding 531 species to the human gut repertoire: 146 bacteria known in humans but not in the gut, 187 bacteria and 1 archaea not previously isolated in humans, and 197 potentially new species. Genome sequencing was performed on the new species. By comparing the results of the metagenomic and culturomic analyses, we show that the use of culturomics allows the culture of organisms corresponding to sequences previously not assigned. Altogether, culturomics doubles the number of species isolated at least once from the human gut.

Culturing the human microbiota and culturomics

The gut microbiota has an important role in the maintenance of human health and in disease pathogenesis. This importance was realized through the advent of omics technologies and their application to improve our knowledge of the gut microbial ecosystem. In particular, the use of metagenomics has revealed the diversity of the gut microbiota, but it has also highlighted that the majority of bacteria in the gut remain uncultured. Culturomics was developed to culture and identify unknown bacteria that inhabit the human gut as a part of the rebirth of culture techniques in microbiology. Consisting of multiple culture conditions combined with the rapid identification of bacteria, the culturomic approach has enabled the culture of hundreds of new microorganisms that are associated with humans, providing exciting new perspectives on host–bacteria relationships. In this Review, we discuss why and how culturomics was developed. We describe how culturomics has extended our understanding of bacterial diversity and then explore how culturomics can be applied to the study of the human microbiota and the potential implications for human health.Culturomics was developed to culture and identify unknown bacteria that inhabit the human gut. In this Review, Raoult and colleagues discuss the development of culturomics and how it has extended our understanding of bacterial diversity, and highlight the potential implications for human health.

“Libanicoccus massiliensis” gen. nov., sp. nov., a new bacterium isolated from a stool sample from a pygmy woman

This study supports the main characteristics of a new genus “Libanicoccus massiliensis” strain Marseille-P3237 (CSURP3237); a new member of the order Coribacteriaceae that was isolated from a stool sample from a healthy 35-year-old pygmy woman.

Libanicoccus massiliensis gen. nov., sp. nov., a new bacterium isolated from human stool

Strain Marseille-P3237 was isolated from a stool sample of a healthy 35-year-old Congolese pygmy female. This anaerobic, Gram-negative, non-spore-forming and non-motile coccus-shaped bacterium is a member of the order Coriobacteriales. It exhibits a 2 009 306-bp genome with a 65.46 mol% G+C content and is closely related to, but distinct from, members of the Olsenella genus. We propose the creation of the new genus Libanicoccus gen. nov. and of the new species Libanicoccus massiliensis sp. nov.

The contribution of culturomics to the repertoire of isolated human bacterial and archaeal species

After a decade of research and metagenomic analyses, our knowledge of the human microbiota appears to have reached a plateau despite promising results. In many studies, culture has proven to be essential in describing new prokaryotic species and filling metagenomic gaps. In 2015, only 2172 different prokaryotic species were reported to have been isolated at least once from the human body as pathogens or commensals. In this review, we update the previous repertoire by reporting the different species isolated from the human body to date, increasing it by 28% to reach a total of 2776 species associated with human beings. They have been classified into 11 different phyla, mostly the Firmicutes, Proteobacteria, Bacteroidetes, and Actinobacteria. Finally, culturomics contributed up to 66.2% towards updating this repertoire by reporting 400 species, of which 288 were novel. This demonstrates the need to continue the culturing work, which seems essential in order to decipher the hidden human microbial content.

“Eggerthella timonensis” gen. nov. isolated from a human stool sample

We report the main characteristics of “Eggerthella timonensis” strain Marseille-P3135 which was isolated from a stool sample of a healthy 8-year-old pygmy (Baka) girl.

“Collinsella bouchesdurhonensis” sp. nov., identified in human stool sample

We report the main characteristics of “Collinsella bouchesdurhonensis” strain Marseille-P3296, which was isolated from a stool sample of a healthy 50-year-old pygmy (Baka) woman.

“Phoenicibacter massiliensis” gen. nov., sp. nov. , a new bacterium isolated from the human gut of a pygmy woman

This study supports the main characteristics of the new genus and new species ‘Phoenicibacter massiliensis’ strain Marseille-P3241T (CSUR P3241), a new bacterium isolated from a stool sample of a healthy 47-year-old pygmy woman.

Sanguibacter massiliensis sp. nov., Actinomyces minihominis sp. nov., Clostridium minihomine sp. nov., Neobittarella massiliensis gen. nov. and Miniphocibacter massiliensis gen. nov., new bacterial species isolated by culturomics from human stool samples

We present the description of Sanguibacter massiliensis sp. nov., Actinomyces minihominis sp. nov., Clostridium minihomine sp. nov., Neobittarella massiliensis gen. nov. and Miniphocibacter massiliensis gen. nov., new bacterial species isolated by culturomics from human stool samples.

Noncontiguous finished genome sequences and descriptions of Actinomyces ihuae, Actinomyces bouchesdurhonensis, Actinomyces urinae, Actinomyces marseillensis, Actinomyces mediterranea and Actinomyces oralis sp. nov. identified by culturomics

The taxonogenomic approach, including the culturomics techniques, is now currently used to isolate and characterize new bacteria. These approaches notably allowed us to discover six new species of the Actinomyces genus: Actinomyces ihuae strain SD1, Actinomyces bouchesdurhonensis strain Marseille-P2825, Actinomyces urinae strain Marseille-P2225, Actinomyces marseillensis strain Marseille-P2818, Actinomyces mediterranea strain Marseille-P3257 and Actinomyces oralis strain Marseille-P3109. Each is the type strain of the corresponding bacterial species. 16S ribosomal RNA gene sequence comparison was used to classify these strains among the Actinomyces genus. These strains are all Gram positive, rod shaped and facultative aerobic. We describe the main characteristics of each bacterium and present their complete genome sequence and annotation.