The invention provides fabZ polypeptides and polynucleotides encoding fabZ polypeptides and methods for producing such polypeptides by recombinant techniques. Also provided are methods for utilizing fabZ polypeptides to screen for antibacterial compounds.

EXAMPLES The examples below are carried out using standard techniques, which are well known and routine to those of skill in the art, except where otherwise described in detail. The examples are illustrative, but do not limit the invention. 
 Example 1 Strain Selection, Library Production and Sequencing The polynucleotide having a DNA sequence given in Table 1 &lsqb;SEQ ID NO:1&rsqb; was obtained from a library of clones of chromosomal DNA of Streptococcus pneumoniae in E. coli. The sequencing data from two or more clones containing overlapping Streptococcus pneumoniae DNAs was used to construct the contiguous DNA sequence in SEQ ID NO:1. Libraries may be prepared by routine methods, for example: Methods 1 and 2 below. Total cellular DNA is isolated from Streptococcus pneumoniae 0100993 according to standard procedures and size-fractionated by either of two methods. Method 1 Total cellular DNA is mechanically sheared by passage through a needle in order to size-fractionate according to standard procedures. DNA fragments of up to 11 kbp in size are rendered blunt by treatment with exonuclease and DNA polymerase, and EcoRI linkers added. Fragments are ligated into the vector Lambda ZapII that has been cut with EcoRI, the library packaged by standard procedures and E. coli infected with the packaged library. The library is amplified by standard procedures. Method 2 Total cellular DNA is partially hydrolyzed with a one or a combination of restriction enzymes appropriate to generate a series of fragments for cloning into library vectors (e.g., RsaI, PalI, AluI, Bshl2351), and such fragments are size-fractionated according to standard procedures. EcoRI linkers are ligated to the DNA and the fragments then ligated into the vector Lambda ZapII that have been cut with EcoRI, the library packaged by standard procedures, and E. coli infected with the packaged library. The library is amplified by standard procedures. Example 2 fabZ Characterization There are four distinct chemical reactions required to complete each round of fatty acid elongation in Escherichia coli, which is the paradigm for dissociated (type II) fatty acid synthase system. The third step of this pathway is the dehydration of the nascent &bgr;-hydroxyacyl-ACP to trans-2-acyl-ACP and this step is catalyzed by FabZ. Specifically, FabZ dehydratase catalyzes the dehydration of short chain and long chain saturated and unsaturated &bgr;-hydroxyacyl-ACP. It does not have isomerase activity therefore it is not involved in the biosynthesis of unsaturated fatty acids. FabZ has been genetically and enzymatically characterized in E. coli which can be found in the following references: Richard J. Heath, Charles O. Rock, Roles of FabA and FabZ b-hydroxyacyl-Acyl Carrier Protein Dehydratases in Escherichia coli Fatty acid Biosynthesis, Journal of Biological Chemistry (1996), 271, 27795-27801; and Mohan, S., Kelly, T. M., Eveland, S. S., Raetz, C. R. H., and Anderson, M. S., (1994) J. Biol. Chem. (1994) 269, 32896-32903.