Hello and welcome to the new series on infectious diseases of the zero to finals podcast.

My name is Tom and in the first episode I'm going to be talking to you about bacteria.

If you want to follow along with written notes on this topic, you can follow along at zero definals.com

slash bacteria or in the infectious diseases

section of the zero definals medicine book. So let's get straight into it. Bacteria are single-celled

organisms and they come in many shapes and sizes and most bacteria are not harmful. However, some are pathogenic and cause infectious diseases.

These pathogenic bacteria are the most relevant to learning medicine, because these are the ones

you're going to be treating on a day-to-day basis. They can be organized into several categories.

You can organize them into aerobic and anaerobic bacteria, and you can

organize them into gram positive and gram negative bacteria. And then there's atypical bacteria

which are slightly different. Learning where the bacteria fall within these categories helps you

to work out which antibiotics will be most effective against them

and what type of infections they're most likely to cause. So aerobic bacteria require oxygen,

whereas anaerobic bacteria do not. Gram positive bacteria have a thick peptidoglycan cell wall that stains with crystal violet staining.

So when you add a stain to the bacteria in a culture dish, you'll find that gram positive

bacteria stain and they go crystal violet color.

Gram negative bacteria don't have this thick cell wall,

and so they don't stain with crystal violet stain,

but they will stain with other stains.

Atypical bacteria cannot be stained or cultured in the normal way,

and this is what makes them atypical.

Bacteria can also be classified based on their shapes.

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