Bloom-forming bacteria heavily invest in anti-phage defense

Abstract

Bacterial blooms are characterized by unusually high cell densities and exceptionally low diversity and can profoundly alter ecosystem function and services. Bacteriophages have long been considered an important cause of mortality in blooms, acting as a mechanism for control. Here, we characterize the viral ecology of a long-lasting estuarine bloom of green sulfur bacteria (Chlorobiota). We combined direct cell and viral counts with metagenomic and metaproteomic data to characterize host and phage activity at different time points. The abundance of virus-like particles (VLPs) decreased at high cell densities, suggesting reduced lytic infection rates. The dominant organism, GSB-TRL01 (genus Prosthecochloris), apparently contained a large conjugative plasmid encoding five different anti-phage defense systems. The organism's genome encoded 13 additional defense systems. Compared to the average of five defense systems per microbial genome, this enrichment suggests robust anti-phage defense capabilities. Proteins from ten different defense systems on GSB-TRL01's genome and four systems from the conjugative plasmid were expressed in the proteome. This suggests that GSB-TRL01 invests heavily in anti-phage defense, leading to reduced lysis at high cell densities and allowing blooms to persist for weeks to months. To determine whether this ability is widespread among bloom forming organisms, we compared genomes of putative bloomers to those of non-blooming organisms. We found that bloomer genomes were significantly enriched with anti-phage defense systems. This challenges traditional paradigms of phage ecology in bloom-forming systems and suggests that microbes adapted to high-density growth may have evolved mechanisms to reduce their susceptibility to phage attack.

Microdiversity drives resilience and niche partitioning in the bloom forming cyanobacteria Limnospira platensis
A. Le Vern, C. Duval, J. Frere +8
bioRxiv22 Oct 2026PreprintAll rights reservedFull textMicrobiologybioRxiv
Phage-Inducible Chromosomal Jumbo Islands (PICJIs) spreading antimicrobial resistance, host-adaptation factors and defense systems, a novel satellite family of nucleus-forming Chimalliviridae
A. Rossignol, K. Praud, M. R. Alexandre +8
bioRxiv3 Nov 2026PreprintAll rights reservedFull textMicrobiologybioRxiv
Retail Frozen Blended Beverages as Vehicles for Opportunistic Antibiotic-Resistant and Biofilm-Forming Bacteria.
Qutaiba Ababneh, Ekhlas Al-Rousan, Ziad Jaradat +5
International journal of microbiology23 Oct 2026Peer-reviewedCC BYFull textSystems & synthetic biologyEurope PMC
Differing patterns in community composition and diversity of biofilm-forming bacteria and fungi along a large salinity gradient
L. Virta, J. Wang, I. Salonen
bioRxiv28 Oct 2026PreprintCC BY-NC-NDFull textEcologybioRxiv
Cyanogenic clovers invest more in rhizobia but do not affect rhizobium evolution
J. Eckberg, J. Lau, K. M. Olsen +1
bioRxiv11 Sep 2026PreprintAll rights reservedFull textEcologybioRxiv

Cite

BibTeX RIS

BibTeX

@misc{weed2026bloomforming,
  title = {{Bloom-forming bacteria heavily invest in anti-phage defense}},
  author = {R. Weed and M. Moynihan and E. Greene and O. L. Mathieson and C. A. Crowley and E. N. Junkins and H. Vanderscheuren and A. M. Jivaji and M. Kleiner and S. E. Ruff},
  howpublished = {bioRxiv},
  year = {2026},
  month = sep,
  doi = {10.64898/2026.09.26.754401},
  url = {https://www.biorxiv.org/content/10.64898/2026.09.26.754401v1},
  note = {CC BY-NC-ND},
}

RIS

TY  - UNPB
TI  - Bloom-forming bacteria heavily invest in anti-phage defense
AU  - R. Weed
AU  - M. Moynihan
AU  - E. Greene
AU  - O. L. Mathieson
AU  - C. A. Crowley
AU  - E. N. Junkins
AU  - H. Vanderscheuren
AU  - A. M. Jivaji
AU  - M. Kleiner
AU  - S. E. Ruff
PY  - 2026
DA  - 2026/09/26
PB  - bioRxiv
DO  - 10.64898/2026.09.26.754401
UR  - https://www.biorxiv.org/content/10.64898/2026.09.26.754401v1
AB  - Bacterial blooms are characterized by unusually high cell densities and exceptionally low diversity and can profoundly alter ecosystem function and services. Bacteriophages have long been considered an important cause of mortality in blooms, acting as a mechanism for control. Here, we characterize the viral ecology of a long-lasting estuarine bloom of green sulfur bacteria (Chlorobiota). We combined direct cell and viral counts with metagenomic and metaproteomic data to characterize host and phage activity at different time points. The abundance of virus-like particles (VLPs) decreased at high cell densities, suggesting reduced lytic infection rates. The dominant organism, GSB-TRL01 (genus Prosthecochloris), apparently contained a large conjugative plasmid encoding five different anti-phage defense systems. The organism's genome encoded 13 additional defense systems. Compared to the average of five defense systems per microbial genome, this enrichment suggests robust anti-phage defense capabilities. Proteins from ten different defense systems on GSB-TRL01's genome and four systems from the conjugative plasmid were expressed in the proteome. This suggests that GSB-TRL01 invests heavily in anti-phage defense, leading to reduced lysis at high cell densities and allowing blooms to persist for weeks to months. To determine whether this ability is widespread among bloom forming organisms, we compared genomes of putative bloomers to those of non-blooming organisms. We found that bloomer genomes were significantly enriched with anti-phage defense systems. This challenges traditional paradigms of phage ecology in bloom-forming systems and suggests that microbes adapted to high-density growth may have evolved mechanisms to reduce their susceptibility to phage attack.
ER  -

Abstract

Related

Cite