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The size of the immune repertoire of bacteria.

ABSTRACT: Some bacteria and archaea possess an immune system, based on the CRISPR-Cas mechanism, that confers adaptive immunity against viruses. In such species, individual prokaryotes maintain cassettes of viral DNA elements called spacers as a memory of past infections. Typically, the cassettes contain several dozen expressed spacers. Given that bacteria can have very large genomes and since having more spacers should confer a better memory, it is puzzling that so little genetic space would be devoted by prokaryotes to their adaptive immune systems. Here, assuming that CRISPR functions as a long-term memory-based defense against a diverse landscape of viral species, we identify a fundamental tradeoff between the amount of immune memory and effectiveness of response to a given threat. This tradeoff implies an optimal size for the prokaryotic immune repertoire in the observational range.

SUBMITTER: Bradde S

PROVIDER: S-EPMC7071851 | biostudies-literature | 2020 Mar

REPOSITORIES: biostudies-literature

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The size of the immune repertoire of bacteria.

Bradde Serena S Nourmohammad Armita A Goyal Sidhartha S Balasubramanian Vijay V

Proceedings of the National Academy of Sciences of the United States of America 20200218 10

Some bacteria and archaea possess an immune system, based on the CRISPR-Cas mechanism, that confers adaptive immunity against viruses. In such species, individual prokaryotes maintain cassettes of viral DNA elements called spacers as a memory of past infections. Typically, the cassettes contain several dozen expressed spacers. Given that bacteria can have very large genomes and since having more spacers should confer a better memory, it is puzzling that so little genetic space would be devoted b ...[more]

PMID: 32071241

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