Bacteria strains?

i was just taught that a lab person knows what kind of bacteria certain bacteria are by looking at the shape...is this true. and if it is, then how are different strains identified? Is it a different strain by its location on the body? obviously i do not know much, so the more information, the more i would enjoy to read the answer. thank you

Bacteria strains?
There are actually two answers to your question ....





Since humans around the world generally make good hosts for bacteria, you will find the same general bacteria in the environment. Working with samples taken from cleanrooms, I have learned that certain morphologies indicate different genera of bacteria. For example ....





-- If I look at a TSA plate used for air sampling and see a bright yellow, large, domed, dull bacteria colony with an entire margin, I would bet it is a Micrococcus ....





-- If I look at the same TSA plate and see a small, white to off-white, glossy, flat topped, entire margin colony, I would state it is most likely a Staphylococcus .....





There are many other bacteria you learn to recognize by sight .... Bacillus species grow certain ways that are very easy to recognize, Staphylococcus tend to be small and 'white', Gram negatives look watery .......





The second part of your question involves the Gram stain. Some bacteria, as you may know, are just there ... nothing too special about them. But, if you showed me slide of an isolate taken from a water sample that has Gram variable cocco-bacillus in 'V' forms .... I would say it is most likely a Coryneform.





Ultimately, it is just being familar with bacteria and their morphologies and characteristics. Like any other job in the world, you learn the signs ...... an Ornithologist can identify a bird by its song, a Herpatologist can tell you the frog by its croak, .....





and a Microbiologist ... well ... we know our bacteria!





Please note one thing --- I don't think anyone can tell the 'strain' of a bacterium simply by looking at it. There are certain tests (i.e.: specific media, chemcial tests, etc) that can be used to isolate a specific strain ...... but most Microbiologist can tell the genus and sometimes the species. The strain must be identified!
Reply:English buddy English no habla jib-ber jab.....
Reply:bacteria come in a few basic shapes....such as rods, spheres, spirals...and they can also congregate together into certain grouping types....bunches like grapes, chains....so, a microbiologist can look at bacteria under a microscope and narrow it down to the type of bacteria under some circumstances. (see this site for pictures of the shapes: http://en.wikipedia.org/wiki/Bacteria) however, you cannot tell one strain of a particular bacteria from another this way, nor can you be totally sure about the type just by looking. when you need to know the exact type of bacteria and strain, there are many different ways of doing it---from low tech to high tech (Gram stains, plating on selective media, ELISA, PCR phenotyping).