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The RcsCDB phosphorelay was originally identified as the main regulator of colanic acid biosynthesis in Escherichia coli K-12. However, recent transcriptomic analyses have identified more than 150 genes belonging to the Rcs regulon, including yjbE, yjbF, yjbG and yjbH. These genes are clustered on the genome and oriented in the same direction but their function remains unknown. In this work it is shown that yjbE, yjbF, yjbG and yjbH are transcribed as a single operon and it is confirmed that the expression of this operon is controlled by the Rcs phosphorelay, in a manner that is dependent on the auxiliary regulatory protein RcsA. Interestingly, Northern blot analysis revealed that the amount of yjbE transcripts in the cell is higher than the amount of yjbEFGH transcripts and it is proposed that this differential expression is mediated by the presence of a strong stem-loop structure in theyjbE-yjbF intergenic region. Finally, evidence is provided that the overexpression of yjbEFGH affects colony morphology and leads to the production of an extracellular polysaccharide that binds Congo red and toluidine blue-O.

Experimental studies confirm that an enzymatically released proteinaceous component of the insect pathogenic fungus Metarhizium anisopliae cuticle exhibits the capacity to induce a cuticle-degrading protease, PR1. PR1 is the major determinant of the pathogenicity of the fungus. Digestion of the cuticle with either PR1 or the trypsin-like PR2 generates peptides in the range 15-2,000 Da.

Metarhizium anisopliae, an insect pathogenic fungus, generalized chymoelastase PR1, which is an extracellular cuticle-degrading proteases determining pathogenicity. A component of insect cuticle induced PR1, which was not a function of fungal growth. This insect pathogenic fungi is used in pest control.

The characterization of extracellular aminopeptidase and dipeptidylpeptidase in culture filtrates of the fungal entomopathogen Metarhizium anisopliae was reported. The aminopeptidase had a M(sub r) 45,000 and a pH optimum of 7, and the dipeptidylpeptidase had a M(sub r) 74,000 and pHoptimum of 8. The aminopeptidase showed optimum activity against Ala-4-methoxy-2-naphthylamine, indicative of an alanyl aminopeptidase (aminopeptidase M). On the other hand, the dipeptidylpeptidase was classified as a prolyl-dipeptidylpeptidase because it releases N-terminal dipeptides from polypeptides containing proline in the penultimate position.

Research shows that aggressive isolates of Trichoderma harzianum produce about 7-8-fold higher biomass in compost, containing Agaricus bisporus, than the nonaggressive isolates. Results indicate that both aggressive isolates secrete depolymerases, which attack the cell walls of A. bisporus. Data suggest that aggressiveness is due to competition, antagonism, or parasitism in a saprophytic growth environment.

This article describes the development of a culture medium for selective, quantitative reisolation of Trichoderma harzianum from commercial Agaricus bisporus compost. The culture medium containing the antimicrobials such as chloramphenicol, streptomycin, quintozene, and propamocarb selectively allows recovery of T. harzianum in the form of viable conidia and hyphal fragments in compact colonies.