scholarly journals Bioenergetics and the Role of Soluble Cytochromescfor Alkaline Adaptation in Gram-Negative AlkaliphilicPseudomonas

2015 ◽  
Vol 2015 ◽  
pp. 1-14 ◽  
Author(s):  
T. Matsuno ◽  
I. Yumoto
Keyword(s):  
Energy Production ◽  
Marked Decrease ◽  
High Electron ◽  
Wild Type ◽  
Gram Negative ◽  
Gram Positive Bacteria ◽  
Aeration Intensity ◽  
Maximum Cell ◽  
Terminal Oxidation

Very few studies have been conducted on alkaline adaptation of Gram-negative alkaliphiles. The reversed difference of H+concentration across the membrane will make energy production considerably difficult for Gram-negative as well as Gram-positive bacteria. Cells of the alkaliphilic Gram-negative bacteriumPseudomonas alcaliphilaAL15-21Tgrown at pH 10 under low-aeration intensity have a soluble cytochromeccontent that is 3.6-fold higher than that of the cells grown at pH 7 under high-aeration intensity. Cytochromec-552 content was higher (64% in all soluble cytochromesc) than those of cytochromec-554 and cytochromec-551. In the cytochromec-552-dificient mutant grown at pH 10 under low-aeration intensity showed a marked decrease inμmax⁡[h−1] (40%) and maximum cell turbidity (25%) relative to those of the wild type. Considering the high electron-retaining abilities of the three soluble cytochromesc, the deteriorations in the growth of the cytochromec-552-deficient mutant could be caused by the soluble cytochromescacting as electron storages in the periplasmic space of the bacterium. These electron-retaining cytochromescmay play a role as electron and H+condenser, which facilitate terminal oxidation at high pH under air-limited conditions, which is difficult to respire owing to less oxygen and less H+.

Influence of the cell wall on ciprofloxacin susceptibility in selected wild-type Gram-negative and Gram-positive bacteria

2004 ◽  
Vol 23 (6) ◽  
pp. 627-630 ◽  
Author(s):  
Mercedes Berlanga ◽  
M.Teresa Montero ◽  
Jordi Hernández-Borrell ◽  
Miquel Viñas
Keyword(s):  
Cell Wall ◽  
Wild Type ◽  
Gram Positive ◽  
Gram Negative ◽  
Gram Positive Bacteria

scholarly journals The Recombination Genes addAB Are Not Restricted to Gram-Positive Bacteria: Genetic Analysis of the Recombination Initiation Enzymes RecF and AddAB in Rhizobium etli

2004 ◽  
Vol 186 (23) ◽  
pp. 7905-7913 ◽  
Author(s):  
Jacobo Zuñiga-Castillo ◽  
David Romero ◽  
Jaime M. Martínez-Salazar
Keyword(s):  
Recombination Frequency ◽  
Double Strand Breaks ◽  
Additive Effect ◽  
Gram Negative Bacteria ◽  
Rhizobium Etli ◽  
Gram Positive ◽  
Gram Negative ◽  
Strand Breaks ◽  
Gram Positive Bacteria

ABSTRACT Single-strand gaps (SSGs) and double-strand breaks (DSBs) are the major initiation sites for recombination. In bacteria, the SSGs are repaired by RecFOR, while the DSBs are processed by RecBCD in gram-negative bacteria and AddAB in gram-positive bacteria. Unexpectedly, instead of recBCD genes, the addAB genes were found in members of the α-proteobacteria group (gram negative). Taking Rhizobium etli as a model, the role of recF and addAB genes in homologous recombination and repair of damaged DNA was evaluated. Inactivation of either recF or addA provoked strong sensitivity to UV radiation and mitomycin C, while an additive effect was observed in the recF-addA mutant. The DSBs generated by nalidixic acid caused low viability only in the addA mutant. The recombination frequency of large and small plasmids was reduced in the recF mutant (24- and 36-fold, respectively), whereas a slight decrease (threefold) in the addA mutant was observed. Moreover, an additive effect (47- and 90-fold, respectively) was observed in the double mutant, but it was not as dramatic as that in a recA mutant. Interestingly, the frequency of deletion and Campbell-type recombination was slightly affected in either single or double mutants. These results suggest that another pathway exists that allows plasmid and Campbell-type recombination in the absence of recF and addA genes.

scholarly journals Functions of the BamBCDE Lipoproteins Revealed by Bypass Mutations in BamA

2020 ◽  
Vol 202 (21) ◽  
Author(s):  
Elizabeth M. Hart ◽  
Thomas J. Silhavy
Keyword(s):  
Membrane Proteins ◽  
Outer Membrane ◽  
Outer Membrane Proteins ◽  
Gram Negative Bacteria ◽  
Wild Type ◽  
Gram Negative ◽  
Bam Complex ◽  
Essential Function ◽  
The Individual

ABSTRACT The heteropentomeric β-barrel assembly machine (BAM complex) is responsible for folding and inserting a diverse array of β-barrel outer membrane proteins (OMPs) into the outer membrane (OM) of Gram-negative bacteria. The BAM complex contains two essential proteins, the β-barrel OMP BamA and a lipoprotein BamD, whereas the auxiliary lipoproteins BamBCE are individually nonessential. Here, we identify and characterize three bamA mutations, the E-to-K change at position 470 (bamAE470K), the A-to-P change at position 496 (bamAA496P), and the A-to-S change at position 499 (bamAA499S), that suppress the otherwise lethal ΔbamD, ΔbamB ΔbamC ΔbamE, and ΔbamC ΔbamD ΔbamE mutations. The viability of cells lacking different combinations of BAM complex lipoproteins provides the opportunity to examine the role of the individual proteins in OMP assembly. Results show that, in wild-type cells, BamBCE share a redundant function; at least one of these lipoproteins must be present to allow BamD to coordinate productively with BamA. Besides BamA regulation, BamD shares an additional essential function that is redundant with a second function of BamB. Remarkably, bamAE470K suppresses both, allowing the construction of a BAM complex composed solely of BamAE470K that is able to assemble OMPs in the absence of BamBCDE. This work demonstrates that the BAM complex lipoproteins do not participate in the catalytic folding of OMP substrates but rather function to increase the efficiency of the assembly process by coordinating and regulating the assembly of diverse OMP substrates. IMPORTANCE The folding and insertion of β-barrel outer membrane proteins (OMPs) are conserved processes in mitochondria, chloroplasts, and Gram-negative bacteria. In Gram-negative bacteria, OMPs are assembled into the outer membrane (OM) by the heteropentomeric β-barrel assembly machine (BAM complex). In this study, we probe the function of the individual BAM proteins and how they coordinate assembly of a diverse family of OMPs. Furthermore, we identify a gain-of-function bamA mutant capable of assembling OMPs independently of all four other BAM proteins. This work advances our understanding of OMP assembly and sheds light on how this process is distinct in Gram-negative bacteria.

Contribution of cysteine residue to the properties of Listeria monocytogenes listeriolysin O

2009 ◽  
Vol 55 (10) ◽  
pp. 1153-1159 ◽  
Author(s):  
Radosław Stachowiak ◽  
Jarosław Wiśniewski ◽  
Olga Osińska ◽  
Jacek Bielecki
Keyword(s):  
Listeria Monocytogenes ◽  
Hemolytic Activity ◽  
Cysteine Residue ◽  
Listeriolysin O ◽  
Wild Type ◽  
Gram Positive Bacteria ◽  
Culture Model ◽  
The Family ◽  
Kinetics Of

Listeriolysin (LLO) is the key virulence factor critical for Listeria monocytogenes pathogenesis. Listerial cytolysin belongs to the family of cholesterol-dependent cytolysins (CDCs), a group of pore-forming toxins produced by related gram-positive bacteria. Most CDCs contain a cysteine residue in the conserved undecapeptide — a sequence that is highly preserved among this group of proteins. Substitutions of cysteine do not always lead to loss of hemolytic activity, questioning the purpose of such strong conservation of this amino acid in the sequence of CDC. The properties of 3 L. monocytogenes strains, a wild type and 2 mutants expressing modified LLO within the cysteine residue, were analyzed in this work. The first of these mutants producing a toxin with cysteine to alanine substitution showed similar features to the wild type except that a thiol-reducing agent was not necessary for hemolytic activity. Another strain secreting LLO containing serine instead of cysteine exhibited strikingly different properties than the wild type. Modified toxin is independent of the reducing reagents, less stable, and shows accelerated kinetics of cytolysis in comparison with the unchanged protein. However, both mutant strains are less invasive in the cell culture model showing the important role of cysteine in L. monocytogenes virulence.

scholarly journals The role of tyrosine-9 and the C-terminal helix in the catalytic mechanism of Alpha-class glutathione S-transferases

1999 ◽  
Vol 343 (3) ◽  
pp. 525-531 ◽  
Author(s):  
Claire S. ALLARDYCE ◽  
Paul D. MCDONAGH ◽  
Lu-Yun LIAN ◽  
C. Roland WOLF ◽  
Gordon C. K. ROBERTS
Keyword(s):  
Conformational Change ◽  
Catalytic Mechanism ◽  
Ethacrynic Acid ◽  
Marked Decrease ◽  
Wild Type ◽  
Wild Type Enzyme ◽  
Turnover Number ◽  
Hydrophobic Substrate ◽  
Glutathione S Transferases

Glutathione S-transferases (GSTs) play a key role in the metabolism of drugs and xenobiotics. To investigate the catalytic mechanism, substrate binding and catalysis by the wild-type and two mutants of GST A1-1 have been studied. Substitution of the ‘essential’ Tyr9 by phenylalanine leads to a marked decrease in the kcat for 1-chloro-2,4-dinitrobenzene (CDNB), but has no affect on kcat for ethacrynic acid. Similarly, removal of the C-terminal helix by truncation of the enzyme at residue 209 leads to a decrease in kcat for CDNB, but an increase in kcat for ethacrynic acid. The binding of a GSH analogue increases the affinity of the wild-type enzyme for CDNB, and increases the rate of the enzyme-catalysed conjugation of this substrate with the small thiols 2-mercaptoethanol and dithiothreitol. This suggests that GSH binding produces a conformational change which is transmitted to the binding site for the hydrophobic substrate, where it alters both the affinity for the substrate and the catalytic-centre activity (‘turnover number‘) for conjugation, perhaps by increasing the proportion of the substrate bound productively. Neither of these two effects of GSH analogues are seen in the C-terminally truncated enzyme, indicating a role for the C-terminal helix in the GSH-induced conformational change.

scholarly journals Modification Strategy of D-leucine Residue Addition on a Novel Peptide from Odorrana schmackeri, with Enhanced Bioactivity and In Vivo Efficacy

Toxins ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 611
Author(s):  
Aifang Yao ◽  
Yingxue Ma ◽  
Xiaoling Chen ◽  
Mei Zhou ◽  
Xinping Xi ◽  
...  
Keyword(s):  
Methicillin Resistant Staphylococcus Aureus ◽  
Therapeutic Potential ◽  
Wild Type ◽  
Anticancer Activities ◽  
Gram Positive Bacteria ◽  
Leucine Residue ◽  
Low Cytotoxicity ◽  
High Cytotoxicity

Brevinins are a well-characterised, frog-skin-derived, antimicrobial peptide (AMP) family, but their applications are limited by high cytotoxicity. In this study, a wild-type des-Leu2 brevinin peptide, named brevinin-1OS (B1OS), was identified from Odorrana schmackeri. To explore the significant role of the leucine residue at the second position, two variants, B1OS-L and B1OS-D-L, were designed by adding L-leucine and D-leucine residues at this site, respectively. The antibacterial and anticancer activities of B1OS-L and B1OS-D-L were around ten times stronger than the parent peptide. The activity of B1OS against the growth of Gram-positive bacteria was markedly enhanced after modification. Moreover, the leucine-modified products exerted in vivo therapeutic potential in an methicillin-resistant Staphylococcus aureus (MRSA)-infected waxworm model. Notably, the single substitution of D-leucine significantly increased the killing speed on lung cancer cells, where no viable H838 cells survived after 2 h of treatment with B1OS-D-L at 10 μM with low cytotoxicity on normal cells. Overall, our study suggested that the conserved leucine residue at the second position from the N-terminus is vital for optimising the dual antibacterial and anticancer activities of B1OS and proposed B1OS-D-L as an appealing therapeutic candidate for development.

The role of biosynthesized silver nanoparticles in antimicrobial mechanisms

2021 ◽  
Vol 22 ◽  
Author(s):  
Bianca PizzornoBackx ◽  
Mayara Santana dos Santos ◽  
Otávio Augusto Leitão dos Santos ◽  
Sérgio Antunes Filho
Keyword(s):  
Silver Nanoparticles ◽  
Green Synthesis ◽  
Antimicrobial Properties ◽  
New Drugs ◽  
Gram Negative Bacteria ◽  
New Materials ◽  
Gram Negative ◽  
Gram Positive Bacteria ◽  
Emergence Of Resistance

: Nanotechnology is an area of science able to develop new materials. The relation between nanotechnology and microbiology is essential for the development of new drugs and vaccines. The main advantage of blend in both areas is to associate the latest technology to obtain new ways to solve problems related to microorganisms. This review seeks to investigate nanoparticle formation's antimicrobial properties, primarily when connected to the green synthesis of silver nanoparticles. The development of new sustainable methods for nanoparticle production has been instrumental in designing alternative, non-toxic, energy-friendly, and environmentally friendly routes. In this sense, it is necessary to study silver nanoparticles' green synthesis concerning their antimicrobial properties. Antimicrobial mechanisms of silver nanoparticles demonstrate efficiency to gram-positive bacteria, gram-negative bacteria, fungi, viruses, and parasites. However, attention is needed with the emergence of resistance to these antimicrobials. This article seeks to relate the parameters of green silver-based nanosystems with the efficiency of antimicrobial activity.

scholarly journals Formation of Methyl Mercaptan froml-Methionine by Porphyromonas gingivalis

2000 ◽  
Vol 68 (12) ◽  
pp. 6912-6916 ◽  
Author(s):  
Mamiko Yoshimura ◽  
Yoshio Nakano ◽  
Yoshihisa Yamashita ◽  
Takahiko Oho ◽  
Toshiyuki Saito ◽  
...  
Keyword(s):  
Porphyromonas Gingivalis ◽  
Wild Type Strain ◽  
Marked Decrease ◽  
Oral Bacteria ◽  
Methyl Mercaptan ◽  
Wild Type ◽  
Oral Malodor ◽  
Gene Encoding ◽  
Degradation Activity

ABSTRACT Methyl mercaptan production by oral bacteria is thought to be one of the main causes of oral malodor. We examined the ability of periodontopathic Porphyromonas gingivalis to produce methyl mercaptan from l-methionine and found that the invasive strains W83 and W50 produced large amounts of methyl mercaptan. We cloned and sequenced the mgl gene encodingl-methionine-α-deamino-γ-mercaptomethane-lyase (METase) from P. gingivalis W83. The structural mgl gene consisted of 1,200 bp and encoded a 43.3-kDa protein. To examine the role of methyl mercaptan in the pathogenesis ofP. gingivalis, a METase-deficient mutant of P. gingivalis W83 was constructed. The methionine degradation activity and virulence of the mutant (M1217) and the parent strain (W83) in mice were compared. M1217 showed a marked decrease in the formation of methyl mercaptan from l-methionine and decreased virulence compared with the wild-type strain W83. These results suggest that methyl mercaptan not only is one of the sources of oral malodor, but may also play a role in the pathogenicity of P. gingivalis.

scholarly journals Lipoproteins of Gram-Positive Bacteria: Key Players in the Immune Response and Virulence

2016 ◽  
Vol 80 (3) ◽  
pp. 891-903 ◽  
Author(s):  
Minh Thu Nguyen ◽  
Friedrich Götz
Keyword(s):  
Immune Response ◽  
Gram Negative Bacteria ◽  
Gram Positive ◽  
Gram Negative ◽  
Content Type ◽  
Gram Positive Bacteria ◽  
Key Players ◽  
Toll Like Receptor 2 ◽  
Number Of Publications

SUMMARYSince the discovery in 1973 of the first of the bacterial lipoproteins (Lpp) inEscherichia coli, Braun's lipoprotein, the ever-increasing number of publications indicates the importance of these proteins. Bacterial Lpp belong to the class of lipid-anchored proteins that in Gram-negative bacteria are anchored in both the cytoplasmic and outer membranes and in Gram-positive bacteria are anchored only in the cytoplasmic membrane. In contrast to the case for Gram-negative bacteria, in Gram-positive bacteria lipoprotein maturation and processing are not vital. Physiologically, Lpp play an important role in nutrient and ion acquisition, allowing particularly pathogenic species to better survive in the host. Bacterial Lpp are recognized by Toll-like receptor 2 (TLR2) of the innate immune system. The important role of Lpp in Gram-positive bacteria, particularly in the phylumFirmicutes, as key players in the immune response and pathogenicity has emerged only in recent years. In this review, we address the role of Lpp in signaling and modulating the immune response, in inflammation, and in pathogenicity. We also address the potential of Lpp as promising vaccine candidates.

Sign in / Sign up

Export Citation Format

Share Document