The 1,852,442-bp sequence of an M1 strain of Streptococcus pyogenes, a Gram-positive pathogen, has been determined and contains 1,752 predicted protein-encoding genes. Approximately onethird of these genes have no identifiable function, with the remainder falling into previously characterized categories of known microbial function. Consistent with the observation that S. pyogenes is responsible for a wider variety of human disease than any other bacterial species, more than 40 putative virulenceassociated genes have been identified. Additional genes have been identified that encode proteins likely associated with microbial ''molecular mimicry'' of host characteristics and involved in rheumatic fever or acute glomerulonephritis. The complete or partial sequence of four different bacteriophage genomes is also present, with each containing genes for one or more previously undiscovered superantigen-like proteins. These prophage-associated genes encode at least six potential virulence factors, emphasizing the importance of bacteriophages in horizontal gene transfer and a possible mechanism for generating new strains with increased pathogenic potential.

The 1,815,783-bp genome of a serotype M49 strain of Streptococcus pyogenes (group A streptococcus [GAS]), strain NZ131, has been determined. This GAS strain (FCT type 3; emm pattern E), originally isolated from a case of acute post-streptococcal glomerulonephritis, is unusually competent for electrotransformation and has been used extensively as a model organism for both basic genetic and pathogenesis investigations. As with the previously sequenced S. pyogenes genomes, three unique prophages are a major source of genetic diversity. Two clustered regularly interspaced short palindromic repeat (CRISPR) regions were present in the genome, providing genetic information on previous prophage encounters. A unique cluster of genes was found in the pathogenicity island-like emm region that included a novel Nudix hydrolase, and, further, this cluster appears to be specific for serotype M49 and M82 strains. Nudix hydrolases eliminate potentially hazardous materials or prevent the unbalanced accumulation of normal metabolites; in bacteria, these enzymes may play a role in host cell invasion. Since M49 S. pyogenes strains have been known to be associated with skin infections, the Nudix hydrolase and its associated genes may have a role in facilitating survival in an environment that is more variable and unpredictable than the uniform warmth and moisture of the throat. The genome of NZ131 continues to shed light upon the evolutionary history of this human pathogen. Apparent horizontal transfer of genetic material has led to the existence of highly variable virulence-associated regions that are marked by multiple rearrangements and genetic diversification while other regions, even those associated with virulence, vary little between genomes. The genome regions that encode surface gene products that will interact with host targets or aid in immune avoidance are the ones that display the most sequence diversity. Thus, while natural selection favors stability in much of the genome, it favors diversity in these regions. Group A streptococcus ([GAS] Streptococcus pyogenes)causes a wide range of human diseases ranging from uncomplicated pharyngitis to life-threatening invasive disease. Acute post-streptococcal glomerulonephritis (APSGN) is one of the nonsuppurative sequelae that can occur following a GAS infection; the other common postinfection sequelae are rheumatic heart disease. Worldwide, it is estimated that approximately 470,000 cases of APSGN occur annually (23). Children and young adults are affected most commonly, with males having twice the incidence as females (74). By the 1940s, evidence was found that streptococcal skin infections were associated with APSGN, and these infections usually did not cause rheumatic fever, leading to the hypothesis that certain GAS strains were "rheumatogenic" while others were "nephritogenic" (41, 72). Further, divergent seasonal patterns of peak incidence exist separating nephritogenic and rheumatogenic GAS, with APSGN cases peaking in the late summer simultaneously with skin infections w...

Over a 9-day period in February 1995, 16 newborn babies (age range 2-11 days) and 3 infants (24, 47 and 180 days of age) in a neonatal nursery ward developed diarrhoea accompanied by pyrexia and weight loss. Known enteropathogens were not detected in their stools but Escherichia coli displaying aggregative adherence to HEp-2 cells (enteroaggregative E. coli) were found in 12 (63%) ill infants and in none of 5 well neonates (P = 0.02). The illness lasted 3-9 days (mean 5.2) in 16 babies, whereas in 3 neonates it showed a protracted course of 18-20 days. The source of infection and the mode of transmission remained unclear. The outbreak isolates manifested properties common in this new group of diarrhoeagenic E. coli: mannose-resistant haemagglutination, haemolysis on blood agar, and clump formation in liquid culture medium. They belonged to the O4 E. coli serogroup and expressed multiple antibiotic resistance.

The cysB gene product is a LysR-type regulatory protein required for expression of the cys regulon. cysB mutants of Escherichia coli and Salmonella, along with being auxotrophs for the cysteine, exhibit increased resistance to the antibiotics novobiocin (Nov) and mecillinam. In this work, by using VplacMu9 insertions creating random lacZ fusions, we identify a gene, hslJ, whose expression appeared to be increased in cysB mutants and needed for Nov resistance. Measurements of the hslJ: :lacZ gene fusion expression demonstrated that the hslJ gene is negatively regulated by CysB. In addition we observe the negative autogenous control of HslJ. When the control imposed by CysB is lifted in the cysB mutant, the elevation of Nov resistance can be achieved only in the presence of wild-type hslJ allele. A double cysB hslJ mutant restores the sensitivity to Nov. Overexpression of the wild-type HslJ protein either in a cysB þ or a cysB 3 background increases the level of Nov resistance indicating that hslJ product is indeed involved in accomplishing this phenotype. The hslJ: :6Kan allele encodes the C-terminaly truncated mutant protein HslJ Q121Ter which is not functional in achieving the Nov resistance but when overexpressed induces the psp operon. Finally, we found that inactivation of hslJ does not affect the increased resistance to mecillinam in cysB mutants.

We demonstrate a new type of soliton formation arising from the interaction of multiple two-dimensional Airy beams in a nonlinear medium. While in linear regime, interference effects of two or four spatially displaced Airy beams lead to accelerated intensity structures that can be used for optical induction of novel light guiding refractive index structures, the nonlinear cross-interaction between the Airy beams decelerates their bending and enables the formation of straight propagating solitary states. Our experimental results represent an intriguing combination of two fundamental effects, accelerated optical beams and nonlinearity, together enable novel mechanisms of soliton formation that will find applications in all-optical light localization and switching architectures. Our experimental results are supported by corresponding numerical simulations.