Insertional mutation of marA vitiates inducible multiple antimicrobial resistance in Salmonella enterica subsp. enterica serovar Choleraesuis

marA has been shown to mediate a multiple antimicrobial resistance (MAR) phenotype following induction in some members of the Enterobacteriaceae. When Salmonella Choleraesuis was exposed to inducing agents they displayed higher minimal inhibitory concentrations (MIC) to multiple antimicrobial agents and an increase in marA expression as determined by northern hybridization analysis. The objective of the present study was to determine if mutation of marA vitiated multiple antimicrobial resistance inducibility in S. Choleraesuis. A loss-of-function mutation of marA in a single S. Choleraesuis isolate was created by insertion of the dihydrofolate reductase (DHFR) gene cassette within marA using double homologous recombination. This mutation was complemented with an expression plasmid possessing marA under the control of an IPTG-inducible promoter. Mutation and complementation of marA was verified using polymerase chain reaction, Northern hybridization, and Western blotting assays. Minimum inhibitory concentrations (MICs) of tetracycline, chloramphenicol, nalidixic acid, and rifampin were determined against induced and uninduced wildtype, marA-disrupted and marA-complemented strains using a microbroth dilution assay. Minimum inhibitory concentrations against induced wildtype and marA-complemented strains increased four- to eight-fold for all antimicrobials tested when compared to the uninduced strains while the MICs of the induced marA-disrupted mutant remained the same. However, this increase was abrogated when the cells were grown in the presence of the efflux pump inhibitor compound EPI phe-arg-naphthylamide. The results indicate that a functional marA is solely required for an inducible multiple antimicrobial resistance phenotype in S. Choleraesuis.     

Soluble protein constituents of the domestic fowl's eggshell.

1. The protein components of the domestic fowl's eggshell are believed to influence appreciably the mechanical properties of the shell and/or its biomineralisation. The purpose of this study was to compare the protein species composing the eggshell matrix in different parts of the shell structure, by SDS-PAGE and chromatography, utilising eggshell cleaned by different methodologies. 2. Protein species were identified whose absence was associated with the removal of the mammillary knobs. In particular, a prominent 81 kDa protein, as well as 38 and 54 kDa calcium-binding proteins, were concentrated within the mammillary layer, as was a 129 kDa insoluble protein. By contrast, soluble proteins of 54, 33, 22, and 14 kDa were enriched in the palisade layer. 3. Our results demonstrate that the mineralised layers of the fowl's eggshell possess a complex array of distinct proteins. The different proteins which have been detected in the mammillary and palisade layers may be related to the distinct crystallisation patterns of calcium carbonate in these zones of the eggshell.     

Using a mixture of microalgae,biochar, and organic manure to increase the capacity of soil to act as carbon sink

Purpose

Microalgae, biochar, or organic manure (OM) can be used as soil amendments to enhance soil organic carbon (OC) content. In the present study, a mixture of all three was used to test whether they could further improve soil OC content and the soil’s ability to retain and fix carbon.

Materials and methods

A laboratory incubation study was carried out to evaluate the efficacy of using microalgae, biochar, OM, or their mixture, as a soil amendment to improve OC in soil extract. Metabolic processes and soil microbial community structuring were analyzed to explore the mechanism by which the mixture increased the capacity of soil to act as a carbon sink.

Results and discussion

OC increased markedly (2.9 times its initial level) following the amendment of the soil with a treatment comprising microalgae, biochar, and the highest dose of OM. Microalgal metabolites were utilized by soil microorganisms as a carbon source. Biochar reduced the concentration of extracellular polysaccharides, whereas OM increased extracellular protein concentration. These metabolites affected the relative proportions of different groups of soil microorganisms, thereby increasing the proportion of Rhodobacter and Runella, which exerted a positive synergistic effect on soil OC and increased the soil’s capacity to fix carbon.

Conclusions

A mixture including microalga, biochar, and OM as a soil amendment improved the OC of soil extract, and its effect was greater than that of any of its components alone. The findings of this study can help in devising ways to increase the OC content and the CO₂-fixing capacity of the soil.

     

Regeneration of alpha-tocopherol in human low-density lipoprotein by green tea catechin.

Oxidative modification of low-density lipoproteins (LDL) may play an important role in the development of atherosclerosis. alpha-Tocopherol functions as a major antioxidant in human LDL. The present study was to test whether green tea catechins (GTC) would protect or regenerate alpha-tocopherol in human LDL. The oxidation of LDL incubated in sodium phosphate buffer (pH 7.4, 10 mM) was initiated by addition of 1.0 mM of 2,2'-azobis(2-amidinopropane) dihydrochloride at 40 degrees C. It was found that alpha-tocopherol was completely depleted within 1 h. Under the same experimental conditions, the longjing GTC extracts demonstrated a dose-dependent protective activity to alpha-tocopherol in LDL at concentrations ranging from 2 to 20 microM. Four pure epicatechin derivatives showed varying protective activity against depletion of alpha-tocopherol in LDL with (-)-epigallocatechin (EGC) and (-)-epigallocatechin gallate (EGCG) being less effective than (-)-epicatechin (EC) and (-)-epicatechin gallate (ECG). The results showed that addition of longjing GTC extracts, EC, ECG, and EGCG at 5, 10, and 15 min to the incubation mixture demonstrated a gradual regeneration of alpha-tocopherol in human LDL.     

Biorefinery-assisted soil management for enhancing food security

Journal of Soils and Sediments - This communication aims to foster the integration of biorefinery and soil management for achieving Sustainable Development Goals (SDGs). The latest advances in...     

Retinal photoreceptor damage produced in guinea pigs by tunicamycin

Corynetoxins, members of the tunicamycin group of antibiotics, produce a severe and frequently fatal neurological disorder in ruminant livestock, and guinea pigs are a useful model to study the pathology and pathogenesis of this disease. The aim of this study was to determine whether tunicamycin produced ocular damage in this species, which could have pharmacotherapeutic and diagnostic value. Four 8-week-old guinea pigs were treated with tunicamycin, and two control animals were given the drug vehicle only. Guinea pigs were injected subcutaneously with 400 μg/kg of tunicamycin, in dimethyl sulphoxide, and killed 48 h post-injection. The eyes were then examined by light microscopy. Immunohistochemistry for rhodopsin was also performed. The principal pathological finding was marked retinal photoreceptor damage, which was characterised by disruption and disorganisation of rods, sometimes progressing to necrosis and separation of the outer segment. The cytoplasm of some rods was focally distended by accumulated, proteinaceous material. Rhodopsin immunopositivity in injured rods was markedly diminished and associated with shrinkage and shortening of the injured rod's outer segment. Ocular pathology, in the form of reproducible and extensive retinal photoreceptor damage, was found in guinea pigs given tunicamycin, extending the range of species found to be susceptible to this toxic injury. The guinea pig could prove to be a good animal model to test potential therapeutic interventions, and as brain lesions are often minimal and liver pathology non-specific in intoxicated ruminants, any spontaneously arising ophthalmic injury found in these species could be diagnostically useful.     

Alzheimer type II astrocytes in the brains of pigs with salt poisoning (water deprivation/intoxication)

The finding of Alzheimer type II astrocytes, in addition to the pathognomonic combination of laminar cerebrocortical necrosis and eosinophil infiltration, in the brains of pigs is reported for the first time in cases of indirect salt poisoning following water deprivation.