<P> Several classes of antibiotics have been designed to target gram - negative bacteria, including aminopenicillins, ureidopenicillins, cephalosporins, beta - lactam - betalactamase combinations (e.g. pipercillin - tazobactam), Folate antagonists, quinolones, and carbapenems . Many of these antibiotics also cover gram positive organisms . The drugs that specifically target gram negative organisms include aminoglycosides, monobactams (aztreonam) and Ciprofloxacin . </P> <P> Gram - negative bacteria display these characteristics: </P> <Ol> <Li> An inner cell membrane is present (cytoplasmic) </Li> <Li> A thin peptidoglycan layer is present (This is much thicker in gram - positive bacteria) </Li> <Li> Has outer membrane containing lipopolysaccharides (LPS, which consists of lipid A, core polysaccharide, and O antigen) in its outer leaflet and phospholipids in the inner leaflet </Li> <Li> Porins exist in the outer membrane, which act like pores for particular molecules </Li> <Li> Between the outer membrane and the cytoplasmic membrane there is a space filled with a concentrated gel - like substance called periplasm </Li> <Li> The S - layer is directly attached to the outer membrane rather than to the peptidoglycan </Li> <Li> If present, flagella have four supporting rings instead of two </Li> <Li> Teichoic acids or lipoteichoic acids are absent </Li> <Li> Lipoproteins are attached to the polysaccharide backbone </Li> <Li> Some contain Braun's lipoprotein, which serves as a link between the outer membrane and the peptidoglycan chain by a covalent bond </Li> <Li> Most, with very few exceptions, do not form spores </Li> </Ol> <Li> An inner cell membrane is present (cytoplasmic) </Li>

The outer membrane of gram-negative cells is primarily composed of
find me the text answering this question