The aquatic microbiome is composed of a multi-phylotype community of microbes, ranging from the numerically dominant viruses to the phylogenetically diverse unicellular phytoplankton. They influence key biogeochemical processes and form the base of marine food webs, becoming food for secondary consumers. Due to recent advances in next-generation sequencing, this previously overlooked component of our hydrosphere is starting to reveal its true diversity and biological complexity. We report here that 250 mL of seawater is sufficient to provide a comprehensive description of the microbial diversity in an oceanic environment. We found that there was a dominance of the order Caudovirales (59%), with the family Myoviridae being the most prevalent. The families Phycodnaviridae and Mimiviridae made up the remainder of pelagic double-stranded DNA (dsDNA) virome. Consistent with this analysis, the Cyanobacteria dominate (52%) the prokaryotic diversity. While the dinoflagellates and their endosymbionts, the superphylum Alveolata dominates (92%) the microbial eukaryotic diversity. A total of 834 prokaryotic, 346 eukaryotic and 254 unique virus phylotypes were recorded in this relatively small sample of water. We also provide evidence, through a metagenomic-barcoding comparative analysis, that viruses are the likely source of microbial environmental DNA (meDNA). This study opens the door to a more integrated approach to oceanographic sampling and data analysis.

This chapter describes the taxonomy of flagellates. Marine flagellates is an all-inclusive term which describes a plethora of different protist species scattered throughout different eukaryotic lineages that move using their flagella. Many flagellates also have other morphological life stages, but the chapter focuses on those taxa for which the flagellated form is predominant. It covers their life cycle, ecology and distribution, and toxic species. It includes a section that indicates the systematic placement of the taxon described within the tree of life, and lists the key marine representative illustrated in the chapter (usually to genus or family level). This section also provides information on the taxonomic authorities responsible for the classification adopted, recent changes which might have occurred, and lists relevant taxonomic sources.

Porcine reproductive and respiratory syndrome virus (PRRSV) causes significant economic losses in the global swine industry, partly because current vaccination strategies offer limited protection against heterologous viral strains. Since modified medium-chain fatty acids (mMCFA) offer enhanced structural stability and antimicrobial properties compared with unmodified MCFA, we evaluated a proprietary mMCFA blend (D-Strike, Devenish Nutrition) against PRRSV in vitro and in vivo. In vitro efficacy was assessed using TCID₅₀ assays on MARC-145 cells and a viability qPCR (V-qPCR). At 1:1000, 1:2000, and 1:5000 dilutions, the mMCFA inactivated >4 logs (99.99%) of the virus within 5 min of exposure. The results of V-qPCR were also compatible with those obtained by cell culture assays. For the in vivo study, 40 weaned male piglets were assigned to four dietary treatments: negative control (group A), PRRSV-challenge control (group B), 0.2% D-Strike (group C), and 0.4% D-Strike (group D). Pigs in groups B, C, and D were challenged intranasally with virulent PRRSV. The results demonstrated that dietary mMCFA reduced clinical signs, attenuated a febrile response, and decreased the severity of lung lesions. Some responses appeared more pronounced at the 0.4% inclusion level than at 0.2%, although a formal dose–response analysis was not statistically significant for most outcome measures. The sera from the 0.4% D-Strike group showed 65% lower PRRSV than the positive control, although this difference was not statistically significant. In addition, this group had 0% mortality as compared to 20% in the positive control group. Feed efficiency also improved in D-Strike-fed pigs. These findings indicate that mMCFA shows promise as a feed additive for mitigating PRRSV infection, although the in vivo antiviral effects require confirmation in larger studies.