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Polycyclic aromatic hydrocarbons (PAHs) are being considered as substances of potential human health hazards due to their resistance toward biodegradation and carcinogenic index. Chrysene is a high molecular weight (HMW)PAHs; the biodegradation of Chrysene using bacteria is recognized as an efficient, environmentally friendly, and cost-effective approach. In our study, a potential chrysene degrading bacterial strain Achromobacter (A.) aegrifaciens was isolated from crude oil-contaminated seawater. A. aegrifaciens was capable of utilizing Chrysene as sole sources of carbon and energy by showing 86% chrysene degradation on day 7, under the conditions of pH 7.0, temperature 30°C, and rotary speed 120 rpm. Bacterial counts have reached a maximum level (over 25 × 1032 CFU/mL). Furthermore, the results revealed that A. aegrifaciens produced biofilm on polystyrene at 20°Cand 30°C, as well as in the air-liquid (A-L) interface. Moreover, A. aegrifaciens were able to swim and to produce biosurfactant with an emulsification activity (E24%) over 10%. Based on the above results, A. aegrifaciens can thus be predicted as a potential candidate for bioremediation of HMW PAHs impacted environments.

Virtually all bacterial species synthesize high levels of (p)ppGpp (guanosine penta- or tetraphosphate), a pleiotropic regulator of the stringent response and other stresses in bacteria. relA and spoT genes are, respectively, involved in synthesis and synthesis/biodegradation of (p)ppGpp. We aimed in this work to evaluate the impact of static magnetic field (SMF) 200 mT exposure on the expression of relA and spoT genes in Salmonella enterica Hadar. Bacteria were exposed to a SMF during 9 h, and RNA extraction was followed by reverse transcriptase polymerase chain reaction (RT-PCR). The relative quantification of mRNA expression levels using the 16S rRNA reference gene did not change during the SMF exposure. However, results showed a significant increase in gene expression for relA after 3 h of exposure (P

The aim of this work is to demonstrate the effects of a static magnetic field (SMF) with an induction 12 equal to 57mT on the viability and membrane lipid composition of Salmonella Hadar. Results showed an increase in the viability of exposed bacteria compared to controls after 9h of exposure. Analysis with gas chromatography of total lipids (TLs) and different fractions of phospholipids: phosphatidylglycerols (PGs), phosphatidylethanolamines (PEs), and cardiolipins (CLs), separated by thin layer chromatography revealed changes in fatty acid levels during exposure. For TLs, the unsaturated fatty acids/saturated fatty acids ratio (UFAs/SFAs) had significantly increased after 9 h of exposure. The variation of this ratio seems to be essentially due to the increase of the proportion of unsaturated fatty acids with 18 carbons, in particular C18:1. The analyses of fatty acid composition carried out on the scale of each fraction of phospholipids showed that CLs contributed significantly to the increase of the proportion of the unsaturated fatty acids between 6 and 9h of exposure thanks to their unsaturated chains with 18 carbons (especially C18:2). CLs appear to be the main phospholipid involved in the adaptation of S. Hadar membranes to the SMF.

We aimed in this work to evaluate the effect of static magnetic field 200 mT (SMF) on the expression of genes involved in the biosynthetic pathway of cardiolipin: g3pd, plsB, cdsA, pgsA, pgpA, cls and phosphatidylethanolamine: pssA and psd in Salmonella enterica subsp enterica serovar Hadar. Bacteria were exposed to a SMF during 3, 6 and 9 h. RNA extraction was followed by Reverse Transcriptase Polymerase Chain Reaction RT-PCR. The relative quantification of mRNA expression levels using 16S rRNA doesn't change during the time exposure. RT-PCR was done for two exposure experiments. The gene expression using RT-PCR present no significant difference in case of plsB, cdsA, pgpA, pgsA and psd genes during the different exposure times. However, a significant increase was observed in the expression of g3pd and pssA genes after 6 h and for cls gene after 3 h of exposure, but any variation was notified after 9 h of exposure. So we can conclude from this study that cls, g3pd and pssA genes are required in the adaptation of Salmonella Hadar to SMF.

We have been interested, in this work, to investigate the effect of the exposure to static magnetic field at 200 mT (SMF) on the fatty acid (FA) composition of Salmonella enterica subsp Enterica serovar Hadar isolate 287: effects on the proportion of saturated and unsaturated fatty acids (SFAs, UFAs), cyclopropane fatty acids (CFAs) and hydroxy fatty acids after exposure to the static magnetic field at 200 mT (SMF). Analysis with Gas Chromatography-Mass Spectrometry (GC-MS) of total lipid showed that the proportion of the most fatty acids was clearly affected. The comparison of UFAs/SFAs ratio in exposed bacteria and controls showed a diminution after 3 and 6 h of exposure. This ration reached a balance after 9 h of treatment with SMF. So we can conclude that S. Hadar tries to adapt to magnetic stress by changing the proportions of SFAs and UFAs over time to maintain an equilibrium after 9 h of exposure, thus to maintain the inner membranes fluidity. Also, a decrease in the proportion of hydroxy FAs was observed after 6 h but an increase of this proportion after 9 h of exposure. Concerning CFAs, its proportion raised after 6 h of exposure to the SMF but it decreased after 9 h of exposure. These results are strongly correlated with those of cfa (cyclopropane fatty acid synthase) gene expression which showed a decrease of its expression after 9 h of exposure.

The present study investigated the adaptation of Salmonella enterica subsp. enterica serovar Hadar to static magnetic field (SMF) exposure (200 mT, 9 h). The proteomic analysis provides an overview of potentially important cytosolic proteins that Salmonella needs to regulate to survive and adapt to magnetic stress. Via 2-dimensional electrophoresis and liquid chromatography tandem mass spectrometry, we compared cytosolic proteomes before and after exposure to magnetic field. A total of 35 proteins displaying more than a 2-fold change were differentially expressed in exposed cells, among which 25 were upregulated and 10 were downregulated. These proteins can be classified mainly into 6 categories: (i) proteins involved in metabolic pathways of carbohydrates, (ii) chaperones and proteins produced in response to oxidative stress, (iii) proteins involved in energy homeostasis, (iv) elongation factors (EF-Tu and EF-Ts), (v) proteins involved in motility, and (vi) proteins involved in molecules transport. Many of the presented observations could be explained, while some represent still-unknown mechanisms. In addition, this study reveals 5 hypothetical proteins. It seems that the stress response to SMF (200 mT) is essentially set up to avoid oxidative damages, with the overexpression of proteins directly involved in oxidative stress response and metabolic switches to counteract oxidative stress. Interestingly, several proteins induced under SMF exposure are found to overlap with those induced by other stresses, such as heat shock and starvation.

The Corynebacterineae represent a distinct group within Gram-positive bacteria, with prominent members being the human pathogens Mycobacterium tuberculosis, Mycobacterium leprae, and Corynebacterium diphtheriae. A common feature of the Corynebacterineae is that they possess an unusual cell wall architecture rich in mycolic acids that is responsible for host pathogenesis and antibiotic resistance. The present study was carried out to evaluate the effects of garlic extract (GE) on the viability, cell wall ultrastructure and fatty acid composition of extractible lipids of Corynebacterium glutamicum. We found that C. glutamicum is inhibited by 44.25 mg ml−1 GE. Observations by electron microscopy revealed that GE alters the cell wall. In addition, GE-treated bacteria (23.6 mg ml−1) showed an increase (from 6.9% to 18.8%) in the extractible lipids released. The fatty acid composition of these lipids was also significantly perturbed, especially C16:0, C18:0, C18:1 and C18:2. These data indicate that the integrity of the cell wall, the most effective target of antimycobacterial drugs, is affected by GE. This knowledge could contribute to improving the treatment of pathogenic Corynebacterineae.

The DNA adenine methylase of Salmonella typhimurium methylates adenine at GATC sequences. Strains deficient in this methylase are not well transformed by methylated plasmids, but unmethylated plasmids transform them at high frequencies. Hemimethylated daughter molecules accumulate after the transformation of dam(-) strains with fully methylated plasmids, suggesting that hemimethylation prevents DNA replication. It will also be shown that plasmids isolated from dam(-) bacteria are hemimethylated by restriction enzyme digestion. These results may explain why newly formed daughter molecules are not substrates for immediate reinitiation of DNA replication in dam(-) bacteria.

When growing cells divide, they need to copy their genetic material and distribute it to en‐ sure that each daughter cell receives one copy. This is a challenging task especially when the enormous length of the DNA compared to the cell size is considered. During DNA replica‐ tion, organization of the chromosomes is even more demanding, since replication forks con‐ tinuously produce new DNA. This DNA contains all the information required to build the cells and tissues of a prokaryotic or an eukaryotic organism. The exact replication of this in‐ formation in any species assures its genetic continuity from generation to generation and is critical to the normal development of an individual. The information stored in DNA is ar‐ ranged in hereditary units known as genes that control the identifiable traits of an organism. Discovery of the structure of DNA and subsequent elucidation of how DNA directs synthe‐ sis of RNA, which then directs assembly of proteins -the so-called central dogma were monumental achievements that marked the early days of molecular biology. However, the simplified representation of the central dogma as DNA → RNA → protein does not reflect the role of proteins in the synthesis of nucleic acids. Moreover, proteins are largely responsi‐ ble for regulating DNA replication and gene expression, the entire process whereby the in‐ formation encoded in DNA is decoded into the proteins that characterize various cell types. Two of these proteins are the DNA adenine methyltransferase (Dam) and the DNA-Binding Protein (SeqA).

Background Salmonella enterica serovar Hadar (S. Hadar) is a highly prevalent foodborne pathogen and therefore a major cause of human gastroenteritis worldwide. Outer membrane proteins whose production is often regulated by environmental conditions also play important roles in the adaptability of bacterial pathogens to various environments. Results The present study investigated the adaptation of S. Hadar under the effect of acute static magnetic field exposure (200 mT, 9 h) and the impact on the outer membrane protein pattern. Via two-dimensional electrophoresis (2-DE) and LC-MS/MS spectrometry, we compared the proteome of enriched-outer membrane fraction before and after exposure to a magnetic field. A total of 11 proteins, displaying more than a two-fold change, were differentially expressed in exposed cells, among which 7 were up-regulated and 4 down-regulated. These proteins were involved in the integrity of cell envelope (TolB, Pal), in the response to oxidative stress (OmpW, dihydrolipoamide dehydrogenase, UspF), in the oxidative stress status (bacterioferritin), in virulence (OmpX, Yfgl) or in motility (FlgE and UspF). Complementary experiments associated the down-regulation of FlgE and UspF with an alteration of swarming, a flagella-driven motility, under SMF. Furthermore, the antibiotic disc diffusion method confirmed a decrease of gentamicin susceptibility in exposed cells. This decrease could be partly associated with the up-regulation of TolC, outer membrane component of an efflux pump. OmpA, a multifunctional protein, was up-regulated. Conclusions SMF (200 mT) seems to maintain the cell envelope integrity and to submit the exposed cells to an oxidative stress. Some alterations suggest an increase of the ability of exposed cells to form biofilms.

article i nfo Article history: This study was carried out to explore the adaptive mechanisms of S. typhimurium particularly, the implication of the Dam methyltransferase in the remodelling of membrane lipid composition to overcome magnetic field stress. With this aim, we focused our analyses on the increase in viable numbers and membrane lipid mod- ifications of S. typhimurium wild-type and dam mutant cells exposed for 10 h to static magnetic fields (SMF; 200 mT). For the wild-type strain, exposure to SMF induced a significant decrease (pb0.05) of CFU at 6 h, followed by an increase between 8 and 10 h. Growth of the dam mutant was significantly affected (pb0.05) after 6 h and no recovery was observed until 10 h, highlighting a different behavior of SMF stressed wild-type and dam mutant strains. SMF significantly affected the phospholipid proportions in the two strains. The most affected were those of the acidic phospholipids, cardiolipins (CL). In the dam strain the phospholip- id response to SMF followed a globally similar trend as in the wild-type with however lower effects, leading mainly to an unusual accumulation of CL. This would in part explain the different behavior of the wild-type and the dam strain. Results showed a significant increase of membrane cyclic fatty acids Cyc17 and Cyc19 in the wild-type strain but only the Cyc17 in the dam strain and a meaningful increase of the total unsaturated fatty acids (UFAs) to total saturated fatty acids (SFAs) ratios of the exposed cells compared to controls from 3 to 9 h (pb0.05) for both strains. The net increase of the total UFAs to total SFAs ratios seemed to result mainly from the increase of (C18:1) proportion (pb0.05) and to a lower extent from that of (C16:1) (pb0.05). These modifications of cyclic and unsaturated fatty acid proportions constitute an adaptive response to SMF stress in S. typhimurium wild-type and dam mutants to maintain an optimum level of membrane fluidity under SMF.

International audience; In the present study, we investigated the effect of exposure to A static magnetic field (SMF) on cell growth, viability, and gene expression of Salmonella enterica subsp. enterica serovar Hadar. Our results indicated that SMF exposure (200 mT, 13 hours) failed to alter cellular growth but induced a decrease of colony-forming units (CFU) between 3 and 6 hours followed by an increase from 6 to 9 hours. The analysis of the differential expression of rpoA, dnaK, katN, and 16S rRNA genes under SMF exposure (200 mT, 10 hours) showed that the expression level of the 16S rRNA mRNA remained stable during the exposure and can thus be used as a reference gene for the analysis on the differential gene expression of Salmonella Hadar. Interestingly, mRNAs of rpoA, katN, and dnaK genes were over-expressed following 10 hours of SMF exposure (200 mT). These data suggest a possible stress response of Salmonella Hadar to static magnetic field.