Nucleotide sequence of rmpB, a Klebsiella pneumoniae gene that positively controls, colanic biosynthesis in Escherichia coli

Multisystemic abscesses in African green monkeys (Chlorocebus aethiops) with invasive Klebsiella pneumoniae--identification of the hypermucoviscosity phenotype

Invasive Klebsiella pneumoniae is an emerging disease of humans characterized by abscesses in the liver or other sites involving bacteria with the unique hypermucoviscosity phenotype. Over several months, 7 African green monkeys in our research colony developed abscess formation in multiple locations and succumbed to disease. K. pneumoniae was identified by bacterial culture in 6 monkeys and immunohistochemistry in 1 additional monkey. All monkeys had been housed in, or had contact with monkeys housed in, 1 animal room in our facility. All affected monkeys had 1 or more abscesses, most notably in the abdomen, but also affecting the lungs, cerebellum, and skin. Abdominal abscesses and associated adhesions entrapped loops of bowel, forming palpable masses. Abdominal masses were located at the root of the mesentery, the ileocecocolic junction, or the pelvic inlet. In 1 case, culture, serotyping, and polymerase chain reaction (PCR) analysis of the bacterial isolate identified K. pneumoniae expressing the hypermucoviscosity phenotype and capsular serotype K2 and determined that the K. pneumonia was genetically rmpA(+)/magA(-).

The Rcs phosphorelay: a complex signal transduction system

RcsC, RcsB, and RcsA were first identified as a sensor kinase, a response regulator, and an auxiliary regulatory protein, respectively, regulating the genes of capsular polysaccharide synthesis. Recent advances have demonstrated that these proteins are part of a complex phosphorelay, in which phosphate travels from the histidine kinase domain in RcsC to a response regulator domain in the same protein; from there to a phosphotransfer protein, RcsD; and from there to RcsB. In addition to capsule synthesis, which requires the unstable regulatory protein RcsA, RcsB also stimulates transcription of a small RNA, RprA; the cell division gene ftsZ; and genes encoding membrane and periplasmic proteins, including the osmotically inducible genes osmB and osmC. The Rcs system appears to play an important role in the later stages of biofilm development; induction of Rcs signaling by surfaces is consistent with this role.

The IS1111 family members IS4321 and IS5075 have subterminal inverted repeats and target the terminal inverted repeats of Tn21 family transposons

IS5075 and IS4321 are closely related (93.1% identical) members of the IS1111 family that target a specific position in the 38-bp terminal inverted repeats of Tn21 family transposons and that are inserted in only one orientation. They are 1,327 bp long and have identical ends consisting of short inverted repeats of 12 bp with an additional 7 bp (TAATGAG) or 6 bp (AATGAG) to the left of the left inverted repeats and 3 bp (AGA) or 4 bp (AGAT) to the right of the right inverted repeat. Circular forms of IS5075 and IS4321 in which the inverted repeats are separated by abutting terminal sequences (AGATAATGAG) were detected. A similar circular product was found for the related ISPa11. Transposition of IS4321 into the 38-bp target site was detected, but a flanking duplication was not generated. The precisely reconstituted target site was also identified. Over 50 members of the IS1111 family were identified. They encode related transposases, have related inverted repeats, and include related bases that lie outside these inverted repeats. In some, the flanking bases number 5 or 6 on the left and 4 or 3 on the right. Specific target sites were found for several of these insertion sequence (IS) elements. IS1111 family members therefore differ from the majority of IS elements, which are characterized by terminal inverted repeats and a target site duplication, and from members of the related IS110 family, which do not have obvious inverted repeats near their termini.

Regulation of expression of group IA capsular polysaccharides in Escherichia coli and related extracellular polysaccharides in other bacteria

Bacterial surface polysaccharides fulfill a number of important roles in cell-cell interactions, survival in natural environments, and formation of biofilms. Consequently, the mechanisms involved in regulation of extracellular polysaccharides are predicted to have a significant impact on microbial adaptation. Strains of Escherichia coli, Klebsiella spp, and Erwinia spp produce extracellular polysaccharides which share structural features. There are also similarities in the organization of genes required for synthesis of these cell surface polymers and, in some cases, the mechanism of synthesis may be related. Despite the diverse habitats of these bacteria, the systems which regulate expression of their extracellular polysaccharides appear to share components and mechanisms. Understanding these regulatory processes may lead to novel therapeutic approaches for pathogens, or for control of unwanted biofilm formation in industrial settings.