The growing demand for reducing chemical inputs in agriculture and increased resistance to insecticides have provided great impetus to the development of alternative forms of insect-pest control. Myco-biocontrol offers an attractive alternative to the use of chemical pesticides. Myco-biocontrol agents are naturally occurring organisms which are perceived as less damaging to the environment. Their mode of action appears little complex which makes it highly unlikely that resistance could be developed to a biopesticide. Past research has shown some promise of the use of fungi as a selective pesticide. The current paper updates us about the recent progress in the field of myco-biocontrol of insect pests and their possible mechanism of action to further enhance our understanding about the biological control of insect pests.

Pseudomonas aeruginosa strains that cause chronic pulmonary infections in cystic fibrosis patients typically undergo mucoid conversion. The mucoid phenotype indicates alginate overproduction and is often due to defects in MucA, an antisigma factor that controls the activity of sigma-22 (AlgT [also called AlgU]), which is required for the activation of genes for alginate biosynthesis. In this study we hypothesized that mucoid conversion may be part of a larger response that activates genes other than those for alginate synthesis. To address this, a two-dimensional (2-D) gel analysis was employed to compare total proteins in strain PAO1 to those of its mucA22 derivative, PDO300, in order to identify protein levels enhanced by mucoid conversion. Six proteins that were clearly more abundant in the mucoid strain were observed. The amino termini of such proteins were determined and used to identify the gene products in the genomic database. Proteins involved in alginate biosynthesis were expected among these, and two (AlgA and AlgD) were identified. This result verified that the 2-D gel approach could identify gene products under sigma-22 control and upregulated by mucA mutation. Two other protein spots were also clearly upregulated in the mucA22 background, and these were identified as porin F (an outer membrane protein) and a homologue of DsbA (a disulfide bond isomerase). Single-copy gene fusions were constructed to test whether these proteins were enhanced in the mucoid strain due to increased transcription. The oprF-lacZ fusion showed little difference in levels of expression in the two strains. However, the dsbA-lacZ fusion showed two-to threefold higher expression in PDO300 than in PAO1, suggesting that its promoter was upregulated by the deregulation of sigma-22 activity. A dsbA-null mutant was constructed in PAO1 and shown to have defects predicted for a cell with reduced disulfide bond isomerase activity, namely, reduction in periplasmic alkaline phosphatase activity, increased sensitivity to dithiothreitol, reduced type IV pilin-mediated twitching motility, and reduced accumulation of extracellular proteases, including elastase. Although efficient secretion of elastase in the dsbA mutant was still demonstrable, the elastase produced appeared to be unstable, possibly as a result of mispaired disulfide bonds. Disruption of dsbA in the mucoid PDO300 background did not affect alginate production. Thus, even though dsbA is coregulated with mucoid conversion, it was not required for alginate production. This suggests that mucA mutation, which deregulates sigma-22, results in a global response that includes other factors in addition to increasing the production of alginate.

Two residues, tyrosine 235 and glutamic acid 237, of the ecotropic murine leukemia virus receptor (ATRC1) have been shown to be essential for receptor-mediated virus envelope binding and entry. We performed genetic analyses to examine the biochemical contribution of these residues in a productive virus-receptor interaction. Altered ATRC1 receptors bearing either a phenylalanine, a tryptophan, a histidine, or a methionine at position 235 mediated ecotropic virus entry comparable to that mediated by ATRC1. In contrast, altered ATRC1 receptors bearing alanine, threonine, serine, or proline at position 235 exhibited a 300-to 10,000-fold decrease in receptor capability. Furthermore, substitution of tyrosine or phenylalanine into the corresponding position (242) of the homologous human protein that lacks ecotropic virus receptor capability resulted in acquisition of ecotropic virus receptor function comparable to that of ATRC1. Substitution of a tryptophan or a histidine at that position of the human protein, however, resulted in a much-reduced receptor capability, suggesting a preference for a benzene ring in the hydrophobic side chain. A similar analysis of proteins substituted at position 237 revealed that aspartic acid, but not arginine or lysine, can functionally substitute for glutamic acid 237 in ATRC1 or at the corresponding position in the human protein. These results suggest a requirement for an acidic and a nearby hydrophobic amino acid for efficient ecotropic virus entry. Similar motifs have been identified in the virus binding sites of other retrovirus receptors, suggesting that the initial step of retrovirus entry may be governed by a common mechanism.

Disulfide bond isomerase proteins (Dsbs) have been extensively characterized in gram-negative bacteria. Recently research efforts is being placed on their biology in gram-positive species. Modern “omics” technologies, allowed assessment of the contribution of the Dsbs to bacterial pathogenesis. The author cloned and characterized the dsbA 1 protein from Pseudomonas aeruginosa in the late 1990s. The global proteome analysis demonstrated that the dsbA gene is under the direct regulatory control of the extracytoplasmic function (ECF) sigma factor AlgT(U) or sigma-22. This is unique to P. aeruginosa. Disruption of dsbA gene results in pleiotropic phenotype: defect in assembly of cysteine disulfide bond containing proteins-as shown in many others. Recently, omics-based approaches identified expression changes in dsbA gene under different physiological states of bacterial pathogens-primarily in free-living, biofilm state, or under infectious disease conditions. Involvement of dsbA function in biofilm formation was shown using dsbA gene disruption mutants. This chapter documents past and current findings and concludes with future trends in research on Dsbs including peptidomimetics.