Microbiology questions?

Question

1) We streak plates and sometimes grow them in liquid broth but how do they really give us pure culture?

2) What can we do with pure cultures?

3) What are the significances of microbial organisation as a community?

4) How do bacteria communicate with each other. Basically explaining to me about the Quorem sensing.

Please only answer if you know because I am studying for a test not to hand up a piece of homework.

The reason why I am asking is because I cannot find an answer to them. I don't care if Jesus hates me or what

Answer 1

You can check into your book.

Answer 2

A pure culture is often grown by using selective media to inhibit the growth of other microorganisms.

Pure cultures are used for study and experiment...gram staining, vaccine research, etc.

Communal living is advantageous because it increases the chances of survival. Living in a group means that a bacterium cannot be singled out and eaten or destroyed...it also means they can act as a unit to accomplish certain tasks such as infection. I'm not sure if division of labor applies to bacteria...I know protists do it. Division of labor is when some organisms focus on food production or locomotion for the benefit of the community.

Bacteria communicate with each other by secreting chemical signals...be they enzymes or whatever. Quorum sensing...just picked that up a little bit ago. When a certain number of bacteria come together they signal each other to start acting...which in the case of pathogenic bacteria lead to disease. A few bacteria won't do any harm, but when the numbers increase they can have a real effect on an organism.