Pre/pro biotic gurus - help me out here

[BeMyV]

Can anyone tell me what the following things do? Lactobacillus acidophilus, Bifidobacterium sp, and Bifidus actiregularis.
I am intrigued to know as I recently started using two products containing these, and I am amazed at the effect it seems to be having on me (feel really light on feet, much more energy, in addition to other changes which might be TMI).
I started these products because I had had 3 courses of antibiotics over 6 weeks and felt I just had wiped out all my good bug colonies. Is this a logical step to have taken?
Any other suggestions as to other -biotics gratefully considered.

Come on come on, roll up!
Someone must know what these things actually do otherwise why are taking them. Or perhaps I am the only one taking them.

I don't know the difference between the 3 you mention.

I usually take acidophillis if I've had an upset stomach or the runs. It just makes my stomach feel right again - helps stop gas, freshens breath, etc. Just gets the digestive system back in kilter. If I was ever given antibiotics I would definitely take them.

We all eat homemade yogurt each day - the starter yogurt we use (rachels yogurt) contains 3 different bacteria. I started to try and help severe ibs. I did start off with shop yogurt but it gets expensive and I was aware of all the little plastic pots we were chucking away. I think it does help, I dont have the problems I used to. We all seem to have pretty healthy tummies. I really miss it when we go away but now I try and have local yogurts when travelling on the (probably misguided) theory that it will help with travellers tummy.