Abstract
Dr. Burk Dehority was an international expert on the classification and monoculture of ruminal ciliated protozoa. We have summarized many of the advancements in knowledge from his work but also in his scientific way of thinking about interactions of ruminal ciliates with the entire rumen microbial community and animal host. As a dedication to his legacy, an electronic library of high-resolution images and video footage catalogs numerous species and techniques involved in taxonomy, isolation, culture, and ecological assessment of ruminal ciliate species and communities. Considerable promise remains to adapt these landmark approaches to harness eukaryotic cell signaling technology with genomics and transcriptomics to assess cellular mechanisms regulating growth and responsiveness to ruminal environmental conditions. These technologies can be adapted to study how protozoa interact (both antagonism and mutualism) within the entire ruminal microbiota. Thus, advancements and limitations in approaches used are highlighted such that future research questions can be posed to study rumen protozoal contribution to ruminant nutrition and productivity.
Highlights
Rumen ciliated protozoa enhance methanogenesis (Newbold et al, 2015) and contribute to proteolysis and to intra-ruminal recycling of microbial protein (Hartinger et al, 2018; Firkins and Mackie, 2020)
The order Vestibuliferida has two main families typically identified in the rumen, with the predominant one being Isotrichidae (Cedrola et al, 2015)
The P-SSU-316F/GIC758R primer set was designed for amplicon sequencing using next-generation sequencing (NGS). It was evaluated for its specificity for rumen protozoa against protozoal reference 18S rRNA gene sequences, including those of non-ruminal ciliates that were available in NCBI (Ishaq and Wright, 2014)
Summary
Rumen ciliated protozoa enhance methanogenesis (Newbold et al, 2015) and contribute to proteolysis and to intra-ruminal recycling of microbial protein (Hartinger et al, 2018; Firkins and Mackie, 2020). Some of the expectation for sequestration by entodiniomorphids is based on interpretation of ‘attachment.’ In contrast with intimate and long-term attachment by other important ruminal microbes such as by cellulolytic bacteria, Dehority (2010) defined attachment as being “closely associated with the insoluble particulate matter.” Second, protozoa traditionally have been expected to be about 50% of the microbial biomass in the rumen and even as high as 70% (Jouany, 1996).
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