scholarly journals Regulation and Adaptive Evolution of Lactose Operon Expression in Lactobacillus delbrueckii

2002 ◽  
Vol 184 (4) ◽  
pp. 928-935 ◽  
Author(s):  
Luciane Lapierre ◽  
Beat Mollet ◽  
Jacques-Edouard Germond
Keyword(s):  
Insertion Sequence ◽  
Selective Pressure ◽  
Constitutive Expression ◽  
Fermented Milk ◽  
Lactobacillus Delbrueckii ◽  
Repressor Gene ◽  
Is Elements ◽  
Gene Insertion ◽  
Palindromic Structure ◽  
Operon Expression

ABSTRACT Lactobacillus delbrueckii subsp. bulgaricus and L. delbrueckii subsp. lactis are both used in the dairy industry as homofermentative lactic acid bacteria in the production of fermented milk products. After selective pressure for the fast fermentation of milk in the manufacture of yogurts, L. delbrueckii subsp. bulgaricus loses its ability to regulate lac operon expression. A series of mutations led to the constitutive expression of the lac genes. A complex of insertion sequence (IS) elements (ISL4 inside ISL5), inserted at the border of the lac promoter, induced the loss of the palindromic structure of one of the operators likely involved in the binding of regulatory factors. A lac repressor gene was discovered downstream of the β-galactosidase gene of L. delbrueckii subsp. lactis and was shown to be inactivated by several mutations in L. delbrueckii subsp. bulgaricus. Regulatory mechanisms of the lac gene expression of L. delbrueckii subsp. bulgaricus and L. delbrueckii subsp. lactis were compared by heterologous expression in Lactococcus lactis of the two lac promoters in front of a reporter gene (β-glucuronidase) in the presence or absence of the lac repressor gene. Insertion of the complex of IS elements in the lac promoter of L. delbrueckii subsp. bulgaricus increased the promoter's activity but did not prevent repressor binding; rather, it increased the affinity of the repressor for the promoter. Inactivation of the lac repressor by mutations was then necessary to induce the constitutive expression of the lac genes in L. delbrueckii subsp. bulgaricus.

scholarly journals Extensive Proliferation of Transposable Elements in Heritable Bacterial Symbionts

2007 ◽  
Vol 190 (2) ◽  
pp. 777-779 ◽  
Author(s):  
Gordon R. Plague ◽  
Helen E. Dunbar ◽  
Phat L. Tran ◽  
Nancy A. Moran
Keyword(s):  
Transposable Elements ◽  
Insertion Sequence ◽  
Early Stage ◽  
Bacterial Symbionts ◽  
Is Elements ◽  
Bacterial Endosymbionts ◽  
Genomic Recombination

ABSTRACT We found that insertion sequence (IS) elements are unusually abundant in the relatively recently evolved bacterial endosymbionts of maize weevils. Because multicopy elements can facilitate genomic recombination and deletion, this IS expansion may represent an early stage in the genomic reduction that is common in most ancient endosymbionts.

Survival of Lactobacillus delbrueckii UFV H2b20 in fermented milk under simulated gastric and intestinal conditions

2013 ◽  
Vol 4 (3) ◽  
pp. 285-289 ◽  
Author(s):  
L.L. da Conceição ◽  
E.S. Leandro ◽  
F.S. Freitas ◽  
M.N.V. de Oliveira ◽  
A.B. Ferreira-Machado ◽  
...  
Keyword(s):  
Gastrointestinal Tract ◽  
Storage Period ◽  
Fermented Milk ◽  
Storage Conditions ◽  
Lactobacillus Delbrueckii ◽  
Refrigerated Storage ◽  
Human Gastrointestinal Tract ◽  
Log Reduction ◽  
Population Reduction ◽  
Potential Use

The survival of Lactobacillus delbrueckii UFV H2b20 was assessed in fermented milk, both during the storage period and after exposure to simulated gastric and intestinal juices, as well the detection of the gene fbpA involved in adherence to human gastrointestinal tract. L. delbrueckii UFV H2b20 remained stable and viable for 28 days under refrigerated storage conditions. After one day of storage, that strain exhibited a one-log population reduction following exposure in tandem to simulated gastric and intestinal juices. After 14 days of storage, a two-log reduction was observed following 90 min of exposure to the simulated gastric conditions. However, the strain did not survive following exposure to the simulated intestinal juice. The observed tolerance to storage conditions and resistance to the simulated gastric and intestinal conditions confirm the potential use of L. delbrueckii UFV H2b20 as a probiotic, which is further reinforced by the detection of fbpA in this strain.

scholarly journals Acquisition of Broad-Spectrum Cephalosporin Resistance Leading to Colistin Resistance in Klebsiella pneumoniae

2016 ◽  
Vol 60 (5) ◽  
pp. 3199-3201 ◽  
Author(s):  
Aurélie Jayol ◽  
Patrice Nordmann ◽  
Marine Desroches ◽  
Jean-Winoc Decousser ◽  
Laurent Poirel
Keyword(s):  
Klebsiella Pneumoniae ◽  
Clinical Isolate ◽  
Broad Spectrum ◽  
Insertion Sequence ◽  
Selective Pressure ◽  
Acquired Resistance ◽  
Colistin Resistance ◽  
Content Type ◽  
Esbl Gene ◽  
Cephalosporin Resistance

ABSTRACTAn extended-spectrum β-lactamase (ESBL)-producing and colistin-resistantKlebsiella pneumoniaeclinical isolate was recovered from a patient who was treated with cefotaxime. This isolate harbored ablaCTX-M-15ESBL gene that was associated with an ISEcp1insertion sequence. Transposition of that tandem occurred within the chromosomalmgrBgene, leading to inactivation of themgrBgene and consequently to acquired resistance to colistin. We showed here a coselection of colistin resistance as a result of a broad-spectrum cephalosporin selective pressure.

scholarly journals Viscometric Properties of Fermented Milk Produced by Ropy Lactobacillus delbrueckii subsp. bulgaricus Strain

1993 ◽  
Vol 64 (3) ◽  
pp. 288-294
Author(s):  
Hitoshi UEMURA ◽  
Mitsuhiko YAMADA ◽  
Takahiro TOBA ◽  
Takatoshi ITOH
Keyword(s):  
Fermented Milk ◽  
Lactobacillus Delbrueckii ◽  
Lactobacillus Delbrueckii Subsp

scholarly journals Transcriptional Regulation oficaADBCby both IcaR and TcaR inStaphylococcus epidermidis

2019 ◽  
Vol 201 (6) ◽  
Author(s):  
Tra-My Hoang ◽  
C. Zhou ◽  
J. K. Lindgren ◽  
M. R. Galac ◽  
B. Corey ◽  
...  
Keyword(s):  
Staphylococcus Epidermidis ◽  
Constitutive Expression ◽  
Skin Surface ◽  
Fine Tuning ◽  
Transcriptional Repressors ◽  
Content Type ◽  
Expression Levels ◽  
Dnase I Footprinting ◽  
Genetic Mechanisms ◽  
Operon Expression

ABSTRACTS. epidermidisis a primary cause of biofilm-mediated infections in humans due to adherence to foreign bodies. A major staphylococcal biofilm accumulation molecule is polysaccharide intracellular adhesin (PIA), which is synthesized by enzymes encoded by theicaADBCoperon. Expression of PIA is highly variable among clinical isolates, suggesting that PIA expression levels are selected in certain niches of the host. However, the mechanisms that govern enhancedicaADBCtranscription and PIA synthesis in these isolates are not known. We hypothesized that enhanced PIA synthesis in these isolates was due to function of IcaR and/or TcaR. Thus, twoS. epidermidisisolates (1457 and CSF41498) with differenticaADBCtranscription and PIA expression levels were studied. Constitutive expression of bothicaRandtcaRdemonstrated that both repressors are functional and can completely repressicaADBCtranscription in both 1457 and CSF41498. However, it was found that IcaR was the primary repressor for CSF41498 and TcaR was the primary repressor for 1457. Further analysis demonstrated thaticaRtranscription was repressed in 1457 in comparison to CSF41498, suggesting that TcaR functions as a repressor only in the absence of IcaR. Indeed, DNase I footprinting suggests IcaR and TcaR may bind to the same site within theicaR-icaAintergenic region. Lastly, we found mutants expressing variable amounts of PIA could rapidly be selected from both 1457 and CSF41498. Collectively, we propose that strains producing enhanced PIA synthesis are selected within certain niches of the host through several genetic mechanisms that function to repressicaRtranscription, thus increasing PIA synthesis.IMPORTANCEStaphylococcus epidermidisis a commensal bacterium that resides on our skin. As a commensal, it protects humans from bacterial pathogens through a variety of mechanisms. However, it is also a significant cause of biofilm infections due to its ability to bind to plastic. Polysaccharide intercellular adhesin is a significant component of biofilm, and we propose that the expression of this polysaccharide is beneficial in certain host niches, such as providing extra strength when the bacterium is colonizing the lumen of a catheter, and detrimental in others, such as colonization of the skin surface. We show here that fine-tuning oficaADBCtranscription, and thus PIA synthesis, is mediated via two transcriptional repressors, IcaR and TcaR.

Deteriorated biofilm-forming capacity and electroactivity of Shewanella oneidnsis MR-1 induced by insertion sequence (IS) elements

2020 ◽  
Vol 156 ◽  
pp. 112136
Author(s):  
Lei Cheng ◽  
Di Min ◽  
Dong-Feng Liu ◽  
Ting-Ting Zhu ◽  
Kai-Li Wang ◽  
...  
Keyword(s):  
Insertion Sequence ◽  
Is Elements

scholarly journals Complete DNA Sequence of Yersinia enterocolitica Serotype 0:8 Low-Calcium-Response Plasmid Reveals a New Virulence Plasmid-Associated Replicon

2001 ◽  
Vol 69 (7) ◽  
pp. 4627-4638 ◽  
Author(s):  
Norma J. Snellings ◽  
Michael Popek ◽  
Luther E. Lindler
Keyword(s):  
Yersinia Enterocolitica ◽  
Insertion Sequence ◽  
Open Reading Frames ◽  
Virulence Plasmid ◽  
Calcium Response ◽  
Is Elements ◽  
New Genes ◽  
Low Calcium ◽  
Reading Frames ◽  
Plasmid Replicons

ABSTRACT The complete nucleotide sequence and organization of theYersinia enterocolitica serotype 0:8 low-calcium-response (LCR) plasmid, pYVe8081, were determined. The 67,720-bp plasmid encoded all the genes known to be part of the LCR stimulon except for ylpA. Eight of 13 intact open reading frames of unknown function identified in pYVe8081 had homologues in Yersinia pestis plasmid pCD1 or inY. enterocolitica serotype 0:9 plasmid pYVe227. A region of approximately 17 kbp showed no DNA identity to pCD1 or pYVe227 and contained six potential new genes, a possible new replicon, and two intact insertion sequence (IS) elements. One intact IS element, ISYen1, was a new IS belonging to the IS256 family. Several vestigial IS elements appeared different from the IS distribution seen in the other LCR plasmids. The RepA proteins encoded by Y. enterocoliticaserotype 0:8 pYVeWA and pYVe8081 were identical. The putative pYVe8081 replicon showed significant homology to the IncL/M replicon of pMU407.1 but was only distantly related to the replicons of pCD1 and pYVe227. In contrast, the putative partitioning genes of pYVe8081 showed 97% DNA identity to the spy/sopABC loci of pCD1 and pYVe227. Sequence analysis suggests thatYersinia LCR plasmids are from a common ancestor but that Y. enterocolitica serotype 0:8 plasmid replicons may have evolved independently via cointegrate formation following a transposition event. The change in replicon structure is predicted to change the incompatibility properties of Y. enterocolitica serotype 0:8 plasmids from those of Y. enterocolitica serotype 0:9 and Y. pestis LCR plasmids.

scholarly journals Microbiological and physical-chemical characteristics of fermented milk beverages

2015 ◽  
Vol 67 (6) ◽  
pp. 1735-1742
Author(s):  
E.H.P. Andrade ◽  
N.M.A. Silva ◽  
M.F.S. Resende ◽  
M.R. Souza ◽  
L.M. Fonseca ◽  
...  
Keyword(s):  
Titratable Acidity ◽  
Fermented Milk ◽  
Lactobacillus Delbrueckii ◽  
Most Probable Number ◽  
Chemical Characteristics ◽  
Salmonella Spp ◽  
Probable Number ◽  
Total Solids ◽  
Physical Chemical ◽  
Belo Horizonte

This study aimed to evaluate some microbiological and physical-chemical characteristics of fermented milk beverages collected at the main supermarkets in Belo Horizonte (MG). 40 samples of the products corresponding to five distinct brands were collected. They were submitted to the following analyses: Most Probable Number (MPN) of total (30ºC) and thermal tolerant coliforms (45ºC), Salmonella spp., coagulase positive Staphylococcus, molds and yeasts, lactic acid bacteria, pH, titratable acidity and contents of moisture, total solids, protein and fat. The analyses were carried out during the last week of shelf life. The microbiological quality of the samples was good and the counts of lactic bacteria were above the minimum established by the official legislation. Streptococcus and Lactobacillus were isolated and identified from the products and Lactobacillus delbrueckii was molecularly identified in three samples. The mean values for the contents of fat and protein, titratable acidity, pH, moisture and total solids ranged from 1.24 to 1.98%; 1.88 to 2.22%; 0.54 to 0.66%; 3.91 to 4.16; 81.18 to 83.25% and 16.75 to 18.82%, respectively. All samples had protein content in agreement with the official legislation.

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