The first detailed images of drug target on the outer wall of bacteria may provide scientists with enough new information to aid design of novel antibiotics. The drugs are much needed to treat deadly infections initiated by Staphylococcus aurous and other bacterial pathogens.   Penicillin and many newer antibiotics work by blocking a piece of the machinery bacteria use to construct their durable outer walls. One end assembles long sugar fibers; the other end stitches them together with bits of protein to form a sturdy interlocking mesh shell.   Enzyme used in the first step of the biochemical pathway that initiates assembly of the sugar coating. The second step is targeted by penicillin and has been well studied.   Although scientists have spent many years identifying bacterial components whose structural features might have weaknesses that can be exploited by antibiotics, progress in turning up bona fide drug targets has been slow.