Cyanobacterial blooms: A player in the freshwater environmental resistome with public health relevance?

Cyanobacterial harmful algal blooms (cyanoHABs) are an ecological concern because of large ecosystem disrupting blooms and a global public health concern because of the cyanotoxins produced by certain bloom forming species. Another threat to global public health is the dissemination of antibiotic resistance (AR) freshwater environmental reservoirs from anthropogenic sources, such as wastewater discharge and urban and agricultural runoff. In this study, cyanobacteria are now hypothesized to play a role in the environmental resistome. A non-systematic literature review of studies using molecular techniques (such as PCR and meta-genomic sequencing) was conducted to explore indirect and direct ways cyanobacteria might contribute environmental AR. Results show cyanobacteria can host antibiotic resistance genes (ARGs) and might promote the spread of ARGs in bacteria due to the significant contribution of mobile genetic elements (MGEs) located genera such as Microcystis. However, cyanobacteria may promote or inhibit the spread of ARGs in environmental freshwater bacteria due to other factors as well. The purpose of this review is to 1) consider the role of cya-nobacteria as AR hosts, since cyanoHABs are historically considered to be a separate problem from AR, and 2) identify the knowledge gap in understanding cyanobacteria as ARG reservoirs. Cyanobacterial blooms, as well other biotic (e.g. interactions with protists or cyanophages) and abiotic factors, should be studied further using advanced methods such as shotgun metagenomic and long read sequencing to clarify the extent of their func-tional ARGs/MGEs and influences on environmental AR.

Automated summary

Cyanobacterial harmful algal blooms and their toxins pose threats to ecosystems and public health, and cyanobacteria may also serve as a reservoir for antibiotic resistance genes. This study conducted a literature review and found that cyanobacteria can host antibiotic resistance genes and contribute to their spread through mobile genetic elements.