Oxidative stress during vitamin A-induced abnormal tail regeneration in the tadpoles of Polypedates maculatus

Vitamin A and its derivatives inhibit normal tail regeneration in amphibians. The most remarkable effect is the development of limbs at the cut end of the tail in anurans. Prior to ectopic limb development, there is an abnormal tail regeneration in the treated tadpoles. The purpose of the present study was to compare oxidative stress condition in the regenerated tail of normal and vitamin A (10I U/ml, 72 h) treated tadpoles. The present findings show a hyper-oxidative stress condition in the regenerated tail of the vitamin A-treated tadpoles of the Indian jumping frog, Polypedates maculatus (Anura: Rhacophoridae).     

Development of cloning vectors and transformation methods for<Emphasis Type="Italic"> Amycolatopsis</Emphasis>

The genus Amycolatopsis is of industrial importance, as its species are known to produce commercial antibiotics. It belongs to the family Pseudonocardiaceae and has an eventful taxonomic history. Initially strains were identified as Streptomyces, then later as Nocardia. However, based on biochemical, morphological and molecular features, the genus Amycolatopsis, containing seventeen species, was created. The development of molecular genetic techniques for this group has been slow. The scarcity of molecular genetic tools including stable plasmids, antibiotic resistance markers, transposons, reporter genes, cloning vectors, and high efficiency transformation protocols has made progress slow, but efforts in the past decade have led to the development of cloning vectors and transformation methods for these organisms. Some of the cloning vectors have broad host range (pRL series) whereas others have limited host range (pMEA300 and pMEA100). The cloning vector pMEA300 has been completely sequenced, while only the minimal replicon (pA-rep) has been sequenced from pRL plasmids. Direct transformation of mycelia and electroporation are the most widely applicable methods for transforming species of Amycolatopsis. Conjugational transfer from Escherichia coli has been reported only in the species A. japonicum, and gene disruption and replacements using homologous recombination are now possible in some strains. Electronic Publication     

Phylogenetic utility of the nuclear gene arginine decarboxylase: an example from Brassicaceae

Arginine decarboxylase (ADC) is an important enzyme in the production of putrescine and polyamines in plants. It is encoded by a single or low-copy nuclear gene that lacks introns in sequences studied to date. The rate of Adc amino acid sequence evolution is similar to that of ndhF for the angiosperm family studied. Highly conserved regions provide several target sites for PCR priming and sequencing and aid in nucleotide and amino acid sequence alignment across a range of taxonomic levels, while a variable region provides an increased number of potentially informative characters relative to ndhF for the taxa surveyed. The utility of the Adc gene in plant molecular systematic studies is demonstrated by analysis of its partial nucleotide sequences obtained from 13 representatives of Brassicaceae and 3 outgroup taxa, 2 from the mustard oil clade (order Capparales) and 1 from the related order Malvales. Two copies of the Adc gene, Adc1 and Adc2, are found in all members of the Brassicaceae studied to data except the basal genus Aethionema. The resulting Adc gene tree provides robust phylogenetic data regarding relationships within the complex mustard family, as well as independent support for proposed tribal realignments based on other molecular data sets such as those from chloroplast DNA.      

Bactericidal Activity of Curcumin I Is Associated with Damaging of Bacterial Membrane

Curcumin, an important constituent of turmeric, is known for various biological activities, primarily due to its antioxidant mechanism. The present study focused on the antibacterial activity of curcumin I, a significant component of commercial curcumin, against four genera of bacteria, including those that are Gram-positive (Staphylococcus aureus and Enterococcus faecalis) and Gram-negative (Escherichia coli and Pseudomonas aeruginosa). These represent prominent human pathogens, particularly in hospital settings. Our study shows the strong antibacterial potential of curcumin I against all the tested bacteria from Gram-positive as well as Gram-negative groups. The integrity of the bacterial membrane was checked using two differential permeabilization indicating fluorescent probes, namely, propidium iodide and calcein. Both the membrane permeabilization assays confirmed membrane leakage in Gram-negative and Gram-positive bacteria on exposure to curcumin I. In addition, scanning electron microscopy and fluorescence microscopy were employed to confirm the membrane damages in bacterial cells on exposure to curcumin I. The present study confirms the broad-spectrum antibacterial nature of curcumin I, and its membrane damaging property. Findings from this study could provide impetus for further research on curcumin I regarding its antibiotic potential against rapidly emerging bacterial pathogens.     

Gradual pediocin PA-1 resistance in <Emphasis Type="Italic">Enterococcus faecalis</Emphasis> confers cross-protection to diverse pore-forming cationic antimicrobial peptides displaying changes in cell wall and mannose PTS expression

Due to innate and acquired resistance in Enterococcus faecalis against most antibiotics, identification of new alternatives has increased interest in diverse populations of potent cationic antimicrobial peptides (CAMPs) for treatment and natural food biopreservation. The CAMPs, after crossing the cell wall to the periplasmic space, kill their target strain by forming pores in the cell membrane. However, reports of resistance against these CAMPs necessitated the understanding of step(s) interfered with while acquiring this resistance, for designing effective CAMP analogs. In this direction, we selected stable and gradual dose-dependent pediocin PA-1 single exposure resistant (Ped^r) mutants of E. faecalis, which conferred cross-protection to diverse CAMPs, viz., HNP-1, nisin and alamethicin but not to polymyxin B, lysozyme and vancomycin. With these Ped^r mutants of E. faecalis there was: a gradual neutralization in cell wall surface charge involving D-alanylation of wall teichoic acids (WTA) and lipoteichoic acids (LTA), increase in cell-surface hydrophobicity, increased cell aggregation and biofilm formation and ultra-structural changes in the cell wall, and a reduction of periplasmic space. In addition, a gradual decrease in expression of mannose PTS two (mpt) operon was also observed with distinct changes in growth rate achieving the same biomass production during the stationary phase. These results show that resistance to these CAMPs is not due to mpt directly acting as a docking molecule but due to changes in the cell wall, which increased the permeability barrier to CAMPs diffusion to reach the periplasmic space.