Dynamics of Baltic Sea phages driven by environmental changes

Abstract

Phage predation constitutes a major mortality factor for bacteria in aquatic ecosystems, and thus, directly impacts nutrient cycling and microbial community dynamics. Yet, the population dynamics of specific phages across time scales from days to months remain largely unexplored, which limits our understanding of their influence on microbial succession. To investigate temporal changes in diversity and abundance of phages infecting particular host strains, we isolated 121 phage strains that infected three bacterial hosts during a Baltic Sea mesocosm experiment. Genome analysis revealed a novel Flavobacterium phage genus harboring gene sets putatively coding for synthesis of modified nucleotides and glycosylation of bacterial cell surface components. Another novel phage genus revealed a microdiversity of phage species that was largely maintained during the experiment and across mesocosms amended with different nutrients. In contrast to the newly described Flavobacterium phages, phages isolated from a Rheinheimera strain were highly similar to previously isolated genotypes, pointing to genomic consistency in this population. In the mesocosm experiment, the investigated phages were mainly detected after a phytoplankton bloom peak. This concurred with recurrent detection of the phages in the Baltic Proper during summer months, suggesting an influence on the succession of heterotrophic bacteria associated with phytoplankton blooms.

Viral challenges and adaptations between Central Arctic Ocean and atmosphere

“…Arctus_1 had a tape measure protein of 978 amino acids length (for sequence see Supplement material). According to a formula proposed earlier [92], the calculated tail length of that phage would be 154.8 nm, which is very close to the length of the phage observed in TEM. Arctica_1 had no identifiable tape tail measure protein.…”

Ecogenomics reveals distinctive viral-bacterial communities in the surface microlayer of a natural surface slick

“…Flavobacterial phages often occur in timely proximity to phytoplankton blooms and heterotrophic bacterial communities following up on such blooms [96], for instance in three consecutive summers at the Linnaeus Microbial Observatory in the Baltic Sea [93]. In addition, we found several flavobacterial (Flaviramulus sp.…”

“…Group 1 comprised a VC from slick SML related to flavobacterial phages as well as the many vOTUs matching to Flavobacteriaceae and Rickettsiaceae MAGs based on k-mer analysis. Flavobacterial phages often occur in timely proximity to phytoplankton blooms and heterotrophic bacterial communities following up on such blooms [96], for instance in three consecutive summers at the Linnaeus Microbial Observatory in the Baltic Sea [93]. In addition, we found several flavobacterial ( Flaviramulus sp.…”

“…In addition, we found another CRISPR spacer from a Paraglaciecola sp. MAG from slick SML matching 104 phages of the genus Barbavirus previously isolated on R. baltica [49,93] (Table S9). In addition, the genome of the bacterial isolate P. tunicata SMS2 and R. baltica SMS4 had a CRISPR array with a spacer of SMS2 matching a 34.8 kb vOTU only detected in the slick SML (Table S9; Supplementary Results).…”

Ecogenomics and cultivation reveal distinctive viral-bacterial communities in the surface microlayer of a Baltic Sea slick

“…In addition, we found another CRISPR spacer from a Paraglaciecola sp. MAG from slick SML matching 104 phages of the genus Barbavirus previously isolated on R. baltica [ 53 , 104 ] (Table S9 ). In addition, the genomes of P. tunicata SMS2 and R. baltica SMS4 had a CRISPR array, with a spacer of SMS2 matching a 34.8 kb vOTU only detected in the slick SML (Table S9 ; Supplementary Results).…”