Reyes-Prieto, A. | Search bioRxiv

bioRxiv2023

Novel lytic and lysogenic cyanophages predicted to infect Microcoleus associated with anatoxin-producing benthic mats

Proliferations of toxic benthic cyanobacteria are increasingly being reported around the world. Of particular concern are Microcoleus-dominated mats associated with anatoxin production that have resulted in dog fatalities. Although the impact of cyanophages has been demonstrated in planktonic systems, their role in the population dynamics of benthic cyanobacteria has received little attention. Here we use metagenomics to explore phage presence in benthic mats from the Wolastoq|Saint John River (WR; New Brunswick, Canada) and Eel River (ER; California, US). Our survey recovered multiple viral-like sequences associated with different putative bacterial hosts, including two cyanophage genomes with apparently different replication strategies. A lysogenic cyanophage (predicted as a prophage) was found integrated in the genomes of Microcoleus sp. 3 recovered from five ER mat samples. This Microcoleus phage is related to previously described Phormidium phage counterparts. Also, we recovered lytic cyanophages from WR and ER mats dominated by anatoxin-producing Microcoleus, which was predicted as the putative host. Despite the geographical distance between WR and ER, the lytic Microcoleus phage genomes recovered from each river have similar sizes (circa 239 Kbp) and share similar gene content with high sequence identity. Phylogenetic analysis suggests that these lytic Microcoleus phages are distant from any other cyanophage previously described. Our results constitute the first report of cyanophages predicted to infect and therefore influence the population dynamics of mat-forming Microcoleus spp. associated with anatoxin production.

microbiology↗

bioRxiv2021

Cytometric Analysis of Diverse Glaucophyte Species Reveals Distinctive Signals Useful for Fluorescence-Based Detection and Sorting

Glaucophytes, red algae and viridiplants (green algae and land plants) are formally united in the supergroup Archaeplastida. Although diverse molecular and genomic evidence suggest the common origin of the three Archaeplastida lineages, the lack of a robust glaucophyte knowledgebase has limited comprehensive evaluations of competing hypotheses. Glaucophytes are rare and apparently confined to freshwater habitats. However, the distribution and diversity of these algae have not been thoroughly explored owing to challenges with detecting and isolating novel specimens. Here we examined the cytometric signatures of representative species of the genera Cyanophora, Cyanoptyche, Glaucocystis and Gloeochaete for a distinctive signal that would aid identification. Most glaucophytes analyzed presented a relatively high red fluorescence signal due to the presence of the blue phycobiliproteins C-phycocyanin and allophycocyanin. Cell-size differences and the concurrent presence of the red phycobiliprotein phycoerythrin in other algal lineages, such as red algae and cryptophytes, allowed us to distinguish glaucophytes from other photosynthetic cells containing blue phycobiliproteins. Our results indicate that the peculiar autofluorescence signal of glaucophytes will facilitate further identification and isolation on novel specimens of this scarce but important algal group.

plant biology↗