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Production of Muramic  -Lactam
in Bacillus subtilis Spore Peptidoglycan.Meghan E. Gilmore, 2004.Bacterial spore heat resistance is primarily dependent upon dehydration of the spore cytoplasm, a state that is maintained by the spore peptidoglycan wall, the spore cortex . A peptidoglycan structural modification found uniquely in spores is the formation of muramic -lactam .
Production of muramic
-lactam
in Bacillus subtilis requires removal of a peptide side chain
from the N-acetylmuramic acid residue by a cwlD-encoded
muramoyl-L-Alanine amidase . Expression of
cwlD takes place in both the mother cell and forespore compartments
of sporulating cells, though expression is expected to be required
only in the mother cell, from which cortex synthesis derives .
Expression of cwlD in the forespore is in a bicistronic message
with the upstream gene ybaK . We show that ybaK plays no
apparent role in spore peptidoglycan synthesis and that expression of
cwlD in the forespore plays no significant role in spore
peptidoglycan formation . Peptide cleavage by CwlD is apparently
followed by deacetylation of muramic acid and lactam ring formation .
The product of pdaA (yfjS), which encodes a putative
deacetylase, has recently been shown to also be required for muramic
-lactam
formation . Expression of CwlD in Escherichia coli results in
muramoyl L-Alanine amidase activity but no muramic
-lactam
formation . Expression of PdaA alone in E . coli had no effect
on E . coli peptidoglycan structure, whereas expression of CwlD
and PdaA together resulted in the formation of muramic
-lactam .
CwlD and PdaA are necessary and sufficient for muramic
-lactam
production, and no other B . subtilis gene product is required .
PdaA probably carries out both deacetylation and lactam ring
formation and requires the product of CwlD activity as a substrate .
Distribution of RuBisCO Genotypes along a Redox Gradient in Mono Lake, California. Bruno J. Giri, 2004.Partial sequences of ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) (EC 4.1.1.39) genes were retrieved from samples taken along a redox gradient in alkaline, hypersaline Mono Lake, Calif . The form I gene (cbbL) was found in all samples, whereas form II (cbbM) was not retrieved from any of the samples . None of the RuBisCO sequences we obtained were closely related (nucleotide similarity, <90%) to sequences in the database . Some could be attributed to organisms isolated from the lake (Cyanobium) or appearing in enrichment cultures . Most (52%) of the sequences fell into in one clade, containing sequences that were identical to sequences retrieved from an enrichment culture grown with nitrate and sulfide, and another clade contained sequences identical to those retrieved from an arsenate-reducing, sulfide-oxidizing enrichment .
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