Strong seasonality and interannual recurrence in marine myovirus communities

Abstract

The temporal community dynamics and persistence of different viral types in the marine environment are still mostly obscure. Polymorphism of the major capsid protein gene, g23, was used to investigate the community composition dynamics of T4-like myoviruses in a North Atlantic fjord for a period of 2 years. A total of 160 unique operational taxonomic units (OTUs) were identified by terminal restriction fragment length polymorphism (TRFLP) of the gene g23. Three major community profiles were identified (winter-spring, summer, and autumn), which resulted in a clear seasonal succession pattern. These seasonal transitions were recurrent over the 2 years and significantly correlated with progression of seawater temperature, Synechococcus abundance, and turbidity. The appearance of the autumn viral communities was concomitant with the occurrence of prominent Synechococcus blooms. As a whole, we found a highly dynamic T4-like viral community with strong seasonality and recurrence patterns. These communities were unexpectedly dominated by a group of persistently abundant viruses.

Fig 1

Rank-abundance plot for the different OTUs observed.

Fig 2

Viral OTUs detected more frequently had higher average and maximum contributions to the T4-like community. Each symbol represents an individual OTU and indicates the OTU's incidence (the number of samples in which it was detected). The x axis shows the average proportion of an OTU, expressed as a percentage of the total amplified products. The y axis shows the maximum observed proportion of the OTU and is also expressed as a percentage of the total amplified myoviral community. (a) Enlarged view of the boxed area on the bottom left. (b) Frequency rank plot for the different OTUs observed.

Fig 3

Temporal TRFLP community structure, showing agreement between two independent approaches. (a) Hierarchical clustering based on SIMPROF permutation tests. Samples connected by red lines could not be significantly differentiated. The black lines indicate significant (P < 0.002) differentiation of clusters. (b) Two-dimensional PCoA analysis ordination of the TRFLP samples. The circled samples correspond to the three major hierarchical clusters presented in the dendrogram in panel a (the similarity threshold was set at 50%).

Fig 4

Individual OTU progression exhibiting three distinct seasonal patterns: winter-spring (OTU 375.8), summer (OTU 372), and autumn (OTU 348.5) (top three charts, respectively). The progression of water temperature and Synechococcus cyanobacterial abundance are plotted in the bottom chart. The gray background gradient corresponds to the three seasonal clusters shown in Fig. 3.