Identification of constraints influencing the bacterial genomes evolution in the PVC super-phylum

Pinos, Sandrine; Pontarotti, Pierre; Raoult, Didier; Merhej, Vicky

doi:10.1186/s12862-017-0921-3

Cited by 1 publication

(1 citation statement)

References 81 publications

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“…The small genomes of Parilichlamydiaceae lack signs of any recent HGT [21], supporting the view that HGT played only a minor part during evolution of chlamydiae residing in vertebrate hosts [76,91]. Chlamydiae associated with arthropods and protists, however, encode a much higher percentage of genes acquired by HGT [78,91,92]. In environmental chlamydiae genes were transferred at the intra-and inter-phylum levels [78,90,92].…”

Section: Horizontal Gene Transfermentioning

confidence: 75%

Chlamydiae in the Environment

Collingro

Köstlbacher

Horn

2020

Trends in Microbiology

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Chlamydiae have been known for more than a century as major pathogens of humans. Yet they are also found ubiquitously in the environment where they thrive within protists and in an unmatched wide range of animals. This review summarizes recent advances in understanding chlamydial diversity and distribution in nature. Studying these environmental chlamydiae provides a novel perspective on basic chlamydial biology and evolution. A picture is beginning to emerge with chlamydiae representing one of the evolutionarily most ancient and successful groups of obligate intracellular bacteria. A Chlamydia for Every EukaryoteChlamydiae are a major cause of eye infections (trachoma) and sexually transmitted disease, being responsible for an estimated 2 million and 130 million infections worldwide per year, respectively [1]. They were originally described as a small, well-separated group of bacteria infecting humans and birds through an unusual and strictly intracellular developmental cycle. During the past two decades, novel chlamydiae have been discovered within protists such as amoebae, and in diverse animal hosts [2,3]. Interchangeably referred to as chlamydia-like organisms (CLOs) or environmental chlamydiae (see Glossary), studying these environmental microbes revealed striking similarities with, and unexpected differences to, the wellknown human pathogens Chlamydia trachomatis, C. pneumoniae, and C.psittaci [2][3][4].A number of review articles have addressed the discovery of these novel chlamydiae, selected aspects of their biology, their interaction with hosts, and their potential role as human and animal pathogens [2][3][4][5][6][7][8][9][10][11][12][13][14]. Here, we focus on accumulating evidence for a widespread occurrence of chlamydiae in diverse environments, as members of various microbiomes, and in a wide range of hoststogether indicating that chlamydiae are indeed ubiquitous in nature. Following the paradigm that (chlamydial) pathogens once originated from environmental bacteria, we highlight recent environmental chlamydia research about fundamental aspects of chlamydial biology, and we show how studying these environmental representatives provides a framework for understanding the evolution of this unique group of intracellular microbes. Microbiome Research Recovers Novel ChlamydiaeOwing to their obligate intracellular lifestyle, chlamydiae are inherently difficult to study and their retrieval directly from environmental samples is challenging. The application of next-generation sequencing techniques in amplicon, single-cell, and metagenome studies has thus been instrumental in investigating chlamydial diversity and biology [15]. Recent technological advances enabled deep sampling as well as deep sequencing, facilitating the recovery of rare taxa in diverse microbiomes and environments. This revealed a hitherto underestimated broad distribution of chlamydiae in nature and a surprisingly high abundance in some habitats [10,[16][17][18][19][20][21][22]. Diversity of Chlamydiae in the EnvironmentRepresentatives...

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