yes some bacteria help aid digestion
In cows and other herbivores, their natural flora of bacteria break down cellulose and make it something they can digest, but in humans our bacteria have no effect on cellulose, so for us it is indigestible.
Herbivorous mammals don't secrete the enzymes required to digest cellulose. They sub-contract the work of cellulose digestion to guest bacteria. The bacteria are provided with a home and lots of food in exchange. Humans don't do this. We have no capacity to digest cellulose. The appendix is the remnant of the Caecum in the human.
fatty acids
Micro-organisms, such as bacteria, are able to digest cellulose. No mammals are able to digest cellulose. This is because cellulose contains a β(1,4) linkage that no mammalian enzyme can break. This is why herbivores must have symbiotic bacteria somewhere in their digestive system that help them break down cellulose.
Digestion
It happens in your Gizzard. The tiny beoglobodas break up the Cellulose with their tiny little beaks
Bacteria is a microorganism, but it possess macro importance in a living body, In the large intestine of herbivores, a bacteria called ''Cellulase'' is present that helps in the digestion of cellulose. Bacteria along with fungi are the major decomposers of biosphere as well. Certain bacteria are also present on our skin, that prevent our skin from drying and protect it as well.
The caecum is the beginning pouch area of the large intestine and is used for digestion of high fiber materials and often serve as storage zones for cellulose digesting bacteria. Since the area is larger the time to fill and pass material is longer.Source(s):http://en.wikipedia.org/wiki/Cecum
Because cattle are ruminants and cellulose is broken down by the microbes found inside of the rumen and then digested further in the cecum. Humans do not have a multiple-chambered stomach nor a functional cecum, thus making digesting cellulose impossible. Cellulose only acts as a gut filler for humans, which is the main reason why plant matter passes through so quickly (in around 2 hours) in a human's digestive tract compared to meat, and compared to the time it takes plant matter to go through a cow's digestive tract.
Let's just put it this way, animals can't live without bacteria. I know that sounds crazy, but there are different kinds of bacteria. The kind that you and I think about a lot are hetatroph bacteria. They cause us to get sick. Autotroph bacteria on the other hand live in you and me inside our intestines. They also live in animals. If we and they didn't have them, we'd die. Hope this helps!
We lack the enzyme cellulase... and we don't have bacteria in our stomachs that do like cows, only bacteria can digest cellulose.