A portion of the nucleotide sequence corresponding to the N-terminal coding region of livJ is essential for its transcriptional regulation

Matsubara, Keiko; Ohnishi, Kouhei; Sadanari, Hidetaka; Yamada, Rie; Fukuda, Shoko

doi:10.1016/s0167-4781(00)00217-7

Cited by 4 publications

(2 citation statements)

References 36 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It is also possible that a negative cis-acting regulatory element is located downstream of the cap8 promoter within the coding region of the 5Ј end of the cap8 operon. Examples of a cis-acting element within the coding region have been reported for other bacteria (3,4,17). Indeed, our preliminary study showed that deletions of this region increased the Pcap1::cap8 promoter activity.…”

Section: Discussionsupporting

confidence: 78%

Overproduction of Type 8 Capsular Polysaccharide AugmentsStaphylococcus aureusVirulence

Luong

Lee

2002

Infect Immun

View full text Add to dashboard Cite

Type 8 capsular polysaccharide (CP8) is the most prevalent capsule type in clinical isolates of Staphylococcus aureus. However, its role in virulence has not been clearly defined. CP8 strains such as strain Becker produce a small amount of capsule on their surface in vitro. In contrast, CP1 strains such as strain M produce a large amount of capsule, which has been shown to be an important antiphagocytic virulence factor. The cap8 and cap1 operons, required for the synthesis of CP8 and CP1, respectively, have been cloned and sequenced. To test whether CP8 contributes to the pathogenesis of S. aureus, we replaced the weak native promoter of the cap8 operon in strain Becker with the strong constitutive promoter of the cap1 operon of strain M. The resultant strain, CYL770, synthesized cap8-specific mRNA at a level about sevenfold higher than that in the parent strain. Remarkably, the CYL770 strain produced about 80-fold more CP8. In a mouse infection model of bacteremia, the CP8-overproducing strain persisted longer in the bloodstream, the liver, and the spleen in mice than the parent strain. In addition, strain CYL770 was more resistant to ospsonophagocytosis in vitro by human polymorphonuclear leukocytes. These results indicate that CP8 is an antiphagocytic virulence factor of S. aureus.For many human pathogens, capsular polysaccharides (CPs) play an important role in bacterial evasion of host immune surveillance, thereby conferring virulence to the pathogens. In Staphylococcus aureus, more than 90% of the strains produce CPs. Among the 11 serotypes of CP identified to date, type 1 CP (CP1), CP2, CP5, and CP8, have been chemically characterized. The repeating units of CP5 and CP8 are almost identical except for the linkages between the amino sugars and the position of the O acetylation. Type 1 and type 2 strains produce a large quantity of capsule. These capsules have been shown to play an important role in virulence. However, type 1 and type 2 strains are rarely isolated clinically. In fact, ϳ53 and ϳ22% of clinical isolates produce CP8 and CP5, respectively. Type 5 and type 8 strains, on the other hand, produce a much smaller amount of capsule than type 1 or type 2 strains in vitro. The small amount of CP5 and CP8 produced by these strains has hampered efforts to define the role of these capsules in virulence. Indeed, several reports concluded that CP5 and CP8 did not confer virulence to S. aureus (see reference 13 for a review). However, recent studies using specific animal models and growth conditions to enhance CP production have shown that CP5 does play a role in the pathogenesis of S. aureus, most probably by evading bacterial uptake and killing by phagocytes (1,18,26). Similar experiments, however, have not been employed to assess the role of CP8 in virulence.The cap1gene cluster, which is required for the synthesis of CP1, has been cloned and sequenced (12, 15). Initial sequencing showed that the cap1 locus was composed of 13 closely linked genes. Recently, we identified two more closely linked cap1 genes...

show abstract

Section: Discussionsupporting

confidence: 78%

Overproduction of Type 8 Capsular Polysaccharide AugmentsStaphylococcus aureusVirulence

Luong

Lee

2002

Infect Immun

View full text Add to dashboard Cite

show abstract

“…ABC transporters are extremely vital in cell viability, virulence and pathogenicity as they function as protein systems that counteract any undesirable changes occurring in the cell [ 37 ]. The periplasmic DppA [ 38 ] (initial receptor for dipeptides transport), artP [ 39 ] (an important component of the arginine binding and transport system) and livJ [ 40 ] (regulator of three branched-chain amino acids system) proteins are some of the major ABC transporters that allow transport of a wide variety of materials across cytoplasmic membranes, and play an important role in bacterial metabolism under conditions of stress. Down regulation of the genes regulating these proteins indicates the inhibition of these bacterial recovery mechanisms.…”

Section: Discussionmentioning

confidence: 99%

Novel pegylated silver coated carbon nanotubes kill Salmonella but they are non-toxic to eukaryotic cells

et al. 2015

View full text Add to dashboard Cite

BackgroundResistance of food borne pathogens such as Salmonella to existing antibiotics is of grave concern. Silver coated single walled carbon nanotubes (SWCNTs-Ag) have broad-spectrum antibacterial activity and may be a good treatment alternative. However, toxicity to human cells due to their physico-chemical properties is a serious public health concern. Although pegylation is commonly used to reduce metal nanoparticle toxicity, SWCNTs-Ag have not been pegylated as yet, and the effect of pegylation of SWCNTs-Ag on their anti-bacterial activity and cell cytotoxicity remains to be studied. Further, there are no molecular studies on the anti-bacterial mechanism of SWCNTs-Ag or their functionalized nanocomposites.Materials and methodsIn this study we created novel pegylated SWCNTS-Ag (pSWCNTs-Ag), and employed 3 eukaryotic cell lines to evaluate their cytotoxicity as compared to plain SWCNTS-Ag. Simultaneously, we evaluated their antibacterial activity on Salmonella enterica serovar Typhimurium (Salmonella Typhimurium) by the MIC and growth curve assays. In order to understand the possible mechanisms of action of both SWCNTs-Ag and pSWCNTs-Ag, we used electron microscopy (EM) and molecular studies (qRT-PCR).ResultspSWCNTs-Ag inhibited Salmonella Typhimurium at 62.5 μg/mL, while remaining non-toxic to human cells. By comparison, plain SWCNTs-Ag were toxic to human cells at 62.5 μg/mL. EM analysis revealed that bacteria internalized either of these nanocomposites after the outer cell membranes were damaged, resulting in cell lysis or expulsion of cytoplasmic contents, leaving empty ghosts. The expression of genes regulating the membrane associated metabolic transporter system (artP, dppA, and livJ), amino acid biosynthesis (trp and argC) and outer membrane integrity (ompF) protiens, was significantly down regulated in Salmonella treated with both pSWCNTs-Ag and SWCNTs-Ag. Although EM analysis of bacteria treated with either SWCNTs-Ag or pSWCNTs-Ag revealed relatively similar morphological changes, the expression of genes regulating the normal physiological processes of bacteria (ybeF), quorum sensing (sdiA), outer membrane structure (safC), invasion (ychP) and virulence (safC, ychP, sseA and sseG) were exclusively down regulated several fold in pSWCNTs-Ag treated bacteria.ConclusionsAltogether, the present data shows that our novel pSWCNTs-Ag are non-toxic to human cells at their bactericidal concentration, as compared to plain SWCNTS-Ag. Therefore, pSWCNTs-Ag may be safe alternative antimicrobials to treat foodborne pathogens.Electronic supplementary materialThe online version of this article (doi:10.1186/s12951-015-0085-5) contains supplementary material, which is available to authorized users.

show abstract

High-level and -yield production of L-leucine in engineered Escherichia coli by multistep metabolic engineering

Ding

Yang

et al. 2023

Metabolic Engineering

View full text Add to dashboard Cite

A portion of the nucleotide sequence corresponding to the N-terminal coding region of livJ is essential for its transcriptional regulation

Cited by 4 publications

References 36 publications

Overproduction of Type 8 Capsular Polysaccharide AugmentsStaphylococcus aureusVirulence

Overproduction of Type 8 Capsular Polysaccharide AugmentsStaphylococcus aureusVirulence

Novel pegylated silver coated carbon nanotubes kill Salmonella but they are non-toxic to eukaryotic cells

High-level and -yield production of L-leucine in engineered Escherichia coli by multistep metabolic engineering

Contact Info

Product

Resources

About