Rumen Microbes – Isotricha species

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To date, we have not talked much about ciliated protozoa. These are a group of microbes characterized by the presence of hair-like extensions on their cell body called cilia. To help remedy this oversight, we will examine a genus of protozoa that are common within the rumen of ruminant animals, Isotricha.

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This interactive image was created by Maddie Henniger

(Image courtesy of

Cattle in a field
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Microscopic image of Isotricha

Isotricha species are holotrich protozoa. This means they are ciliates and have tiny hair-like structures called cilia distributed around them and the cilia are of even length. Image courtesy of the USDA. 

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Flowchart of Microbial Protein Cycles

Generally, protozoal communities in the rumen are known for their ability to prey upon bacteria contributing to the intra-ruminal recycling of microbial protein. However, it has been demonstrated that holotrich protozoa engulf only a very small number of rumen bacteria. Image courtesy of Bach et al., 2005. Journal of Dairy Science, 88, pp.E9-E21. 

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Flowchart of the Biohydrogenation Process

Isotricha prostoma is found in the rumen of cattle and may slightly be involved with bacterial biohydrogenation in the rumen. However, the bacteria associated (endo- and ectosymbionts) with this protozoan or engulfed by I. prostoma could be responsible for the observed results. Image courtesy of

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Microscopic image of Isotricha

While protozoal communities are generally considered to reduce nitrogen utilization efficiency, Isotricha species have a smaller impact on decreasing nitrogen utilization efficiency than other protozoa. Image courtesy of 

Follow this link to view all of the interactive presentations for the Rumen Microbes series.