Colony morphology of four bacteria: E.coli (Gram-negative rods), P.aeruginosa (Gram-negative rods), S.aureus (Gram-positive cocci; colony surrounded by a zone of beta-hemolysis) and S.epidermidis (Gram-positive cocci) on blood agar.
There are many classes of antibiotics. It is useful to know at least a handful of antibiotics, and what they are useful for. Below we attempt to summarise the main types of antibiotics, their mechanisms.
An old antibiotic called octapeptin could help develop new drugs against extensively drug-resistant Gram-negative bacteria.
O Clue: a structural difference between Gram + and Gram - bacteria Outer membrane: Outer membranes are present in gram negative bacteria. The outer membrane is relatively permeable and protects the bacteria from a harsh environment.