Difference Between Bacteria and Active Dry Yeast
Active dry yeast (live) and bacteria are currently utilized in modern beef and dairy production and are commonly grouped under the term probiotic (for life). There are however distinct differences between these organisms. The most obvious is how they are classified. Live yeasts are classified into the kingdom of Eukaryotes which also contains animals, plants and fungi. These organisms are characterized as having a membrane bound nucleus. In comparison, bacteria fall in a completely different kingdom known as the Prokaryotes, which is characterized by the absence of a nucleus. Other distinct differences between yeast and bacteria are shown in the table below.
| Yeast |
Bacteria |
| Eukaryote |
Prokaryote |
| Large (8 to10 microns) |
Small (0.2 to 5 microns) |
| Passes through GI tract |
May grow and colonize GI tract |
| Thicker cell wall |
Thinner cell wall |
| Ferment only sugar and starch |
Ferment various types of compounds |
| Facultative anaerobes (scavenge oxygen) |
Many are strict anaerobes |
| Fermentation yields CO2 and alcohol |
Fermentation yields volatile fatty acids |
| Reproduces through budding and spore production |
Reproduces through binary fission |
| Do not have to be refrigerated for viability |
Most bacteria must be refrigerated to maintain viability |
While the classification and physical/chemical properties are important, the proposed modes of action for improving animal performance should also be considered.
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