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The Architecture of the Murein (Peptidoglycan) in Gram-Negative Bacteria: Vertical Scaffold or Horizontal Layer(s)?. Waldemar Vollmer, 2004. Regulation of Tetralin Biodegradation and Identification of Genes Essential for Expression of thn Operons. O. Martínez-Pérez, 2004.The tetralin biodegradation genes of Sphingomonas macrogolitabida strain TFA are clustered in two closely linked and divergent operons . To analyze expression of both operons under differentgrowth conditions, transcriptional and translational gene fusionsof the first genes of each operon to lacZ have been constructedin plasmids unable to replicate in Sphingomonas and integratedby recombination into the genome of strain TFA . Expression analysis indicated that the transcription of both genes is induced insimilar ways by the presence of tetralin . Gene expression inboth operons is also subjected to overimposed catabolic repression.Two additional genes named thnR and thnY have been identified downstream of thnCA3A4 genes . ThnR is similar to LysR-type regulators, and mutational analysis indicated that ThnR is strictly required for expression of the thn operons . Unlike other LysR-type regulators,ThnR does not repress its own synthesis . In fact, ThnR activatesits own expression, since thnR is cotranscribed with the thnCA3A4genes . ThnY is similar to the ferredoxin reductase componentsof dioxygenase systems and shows the fer2 domain, binding aCys4[2Fe-2S] iron sulfur center, and the FAD-binding domain,common to those reductases . However, it lacks the NAD-bindingdomain . Intriguingly, ThnY has a regulatory role, since it isalso strictly required for expression of the thn operons . Giventhe similarity of ThnY to reductases and the possibility ofits being present in the two redox states, it is tempting tospeculate that ThnY is a regulatory component connecting expressionof the thn operons to the physiological status of the cell. Global Transcriptional Analysis of clpP Mutations of Type 2 Streptococcus pneumoniae and Their Effects on Physiology and Virulence. Gregory T. Robertson, 2002.Streptococcus pneumoniae is an important human pathogen that contains single copies of genes encoding the ClpP and FtsH ATP-dependent proteases but lacks the Lon and HslV proteases . We constructed and characterized the phenotypes of clpP, clpC, and clpX deletion replacement mutants, which lack the ClpP protease subunit or the putative ClpC or ClpX ATPase specificity factor . A  clpP mutant, but not a
clpC or
clpX mutant, of the virulent D39 type 2 strain of S . pneumoniae grew poorly at 30°C and failed to grow at 40°C . Despite this temperature sensitivity, transcription of the heat shock regulon determined by microarray analysis was induced in a
clpP mutant, which was also more sensitive to oxidative stress by H2O2 and to puromycin than its clpP+ parent strain . A
clpP mutant, but not a
clpC mutant, was strongly attenuated for virulence in the murine lung and sepsis infection models . All of these phenotypes were complemented in a
clpP/clpP+ merodiploid strain . Consistent with these complementation patterns, clpP was found to be in a monocistronic operon, whose transcription was induced about fivefold by heat shock in S . pneumoniae as determined by Northern and real-time reverse transcription-PCR analyses . Besides clpP, transcription of clpC, clpE, and clpL, but not clpX or ftsH, was induced by heat shock or entry into late exponential growth phase . Microarray analysis of
clpP mutants showed a limited change in transcription pattern ( 80 genes) consistent with these phenotypes, including repression of genes involved in oxidative stress, metal ion transport, and virulence . In addition, transcription of the early and late competence regulon was induced in the
clpP mutant, and competence gene expression and DNA uptake seemed to be constitutively induced throughout growth . Together, these results indicate that ClpP-mediated proteolysis plays a complex and central role in numerous pneumococcal stress responses, development of competence, and virulence .
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