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The Mormon cricket (MC), Anabrus simplex Haldeman, 1852 (Orthoptera: Tettigoniidae), has a long and negative history with agriculture in Utah and other western states of the USA. Most A. simplex populations migrate in large groups, and their feeding can cause significant damage to forage plants and cultivated crops. Chemical pesticides are often applied, but some settings (e.g. habitats of threatened and endangered species) call for non-chemical control measures. Studies in Africa, South America, and Australia have assessed certain isolates of Metarhizium acridum as very promising pathogens for Orthoptera: Acrididae (locust) biocontrol. In the current study, two isolates of Metarhizium robertsii, one isolate of Metarhizium brunneum, one isolate of Metarhizium guizhouense, and three isolates of M. acridum were tested for infectivity to MC nymphs and adults of either sex. Based on the speed of mortality, M. robertsii (ARSEF 23 and ARSEF 2575) and M. brunneum (ARSEF 7711) were the most virulent to instars 2 to 5 MC nymphs. M. guizhouense (ARSEF 7847) from Arizona was intermediate and the M. acridum isolates (ARSEF 324, 3341, and 3609) were the slowest killers. ARSEF 2575 was also the most virulent to instar 6 and 7 nymphs and adults of MC. All of the isolates at the conidial concentration of 1 × 107 conidia ml−1 induced approximately 100% mortality by 6 days post application of fungal conidia. In conclusion, isolates ARSEF 23, ARSEF 2575, and ARSEF 7711 acted most rapidly to kill MC under laboratory conditions. The M. acridum isolates, however, have much higher tolerance to heat and UV-B radiation, which may be critical to their successful use in field application. [ABSTRACT FROM AUTHOR]

A comparative anlysis of depolymerases produced by saprophytes and opportunists and pathogens of plants, insects and fungi was conducted to determine the adaptation of proteases and carbohydrases to different ecological niches. Results indicate that the pathogens showed enzymic adaptation to the polymers present in the integuments of their particular hosts. The plant pathogens produced high levels of polysaccharide degrading enzymes while the entomopathogens degraded a broad spectrum of proteins. However, the saprophytes and opportunistic pathogens produced the broadest spectrum of protein and polysaccharide degrading enzymes.

Mycoinsecticides are being used for the control of many insect pests as an environmentally acceptable alternative to chemical insecticides. A key aim of much recent work has been to increase the speed of kill and so improve commercial efficacy of these biocontrol agents. This might be achieved by adding insecticidal genes to the fungus, an approach considered to have enormous potential for the improvement of biological pesticides. We report here the development of a genetically improved entomopathogenic fungus. Additional copies of the gene encoding a regulated cuticle-degrading protease (Pr1) from Metarhizium anisopliae were inserted into the genome of M. anisopliae such that Pr1 was constitutively overproduced in the hemolymph of Manduca sexta, activating the prophenoloxidase system. The combined toxic effects of Pr1 and the reaction products of phenoloxidase caused larvae challenged with the engineered fungus to exhibit a 25% reduction in time of death and reduced food consumption by 40% compared to infections by the wild-type fungus. In addition, infected insects were rapidly melanized, and the resulting cadavers were poor substrates for fungal sporulation. Thus, environmental persistence of the genetically engineered fungus is reduced, thereby providing biological containment.

Two isoforms of proteinase 2 (Pr2), the fungal serine proteinase, are secreted by infection structures on the cuticles of cockroaches. The two trypsin components with isoelectric points of 4.4 and 4.9 are separated by analytical and preparative isoelectric focusing methods. Two-dimensional gelatin-sodium dodecyl sulfate-polyacrylamide gel electrophoresis and enzyme overlay membranes are used to analyze the catalytic properties of the proteases. The Pr2 isoforms attack at the carboxyl sides of positively charged amino acids.

Chitinases from the Metarhizium anisopliae (M. anisopliae), Metarhizium flavoviride and Beauveria bassiana species of entomopathogenic fungi have been characterized and ultrastructurally localized. The fungi were observed during fungal invasion of host (Manducta sexta) cuticle. An acidic chitinase was found to be produced by M. anisopliae during penetration of the cuticle. Data indicated that chitinase release is dependent on the accessibility of its substrate.

The fungus Beauveria bassiana has an inner cell wall under its conidial rodlet layer that yielded two types of proteins after extraction by formic acid. The extracted proteins were resolved to be one protein after it was oxidized and treated with SDS, and then was designated cell wall protein 1. In B. bassiana, the protein is typically found only on the conidia but not on the blastopores. Another SDS-insoluble protein, hydrophobin, is found in the outermost rodlet layer of B. bassiana conidia.

Germination of Metarhizium anisopliae strains 808 and 549 differs in its responses to cyclic AMP, 3-isobutyl-1-methylnanthine (IBMX), alanine and glucose. Conidia of 808 strain germinate in alanine but not on glucose or IBMX, while 549 strain germinate in glucose, alanine and IBMX. Both strains have different catabolite-repressing processes. Strains germinating on glucose are sensitive and resistive to 2-deoxyglucose.

The mycelial extract of the fungus Metarhizium flovoviride yields the unique insect toxins viridoxins A and B. Spectroscopic and X-ray studies show that the two diterpenes consist of a hydronaphthyl ring system to which is attached a gamma-pyrone, an alpha-hydroxy-4(3)-methylpentanoate and a 4-methyl-3-pentenyl side chain. Both have the molecular formula C34H52O6 and are differentiated by the position of a methyl group at C-3' (in A) and at C-4' (in B). Their absolute configuration is also presented.

The peptide structure of efrapeptins C to G contains a bicyclic amine at the C-terminus that significantly affects the ATPase inhibitory and insecticidal activity of the peptides. The amino acid sequence of the peptides shows that the structure constitutes 15 amino acid units possessing an acetylated N-terminus. Spectral and chromatographic analyses have determined the structural configuration and the presence of the amino acid residues and acidic fragments that comprise the peptides. In addition, the efrapeptins' lack of any free amino, hydroxyl or carbonyl functionalities makes it inactive to acetylation, Edman degradation, dansylation and CH2N2 reactions.

The aim of the present study was to analyze ten native Metarhizium spp. isolates as to their UV‐B tolerances. Comparisons included: different fungal propagules (conidia, blastospores, or microsclerotia [MS]); conidia in aqueous suspensions or in 10% mineral oil‐in‐water emulsions; and conidia mixed with different types of soil. The UV‐B effect was expressed as the germination of conidia or culturability of blastospores and MS relative to nongerminated propagules. Metarhizium anisopliae LCM S05 exhibited high tolerance as blastospores and/or MS, but not as conidia; LCM S10 and LCM S08 had positive results with MS or conidia but not blastospores. The formulations with 10% mineral oil did not always protect Metarhizium conidia against UV‐B. Conidia of LCM S07, LCM S08, and LCM S10 exhibited the best results when in aqueous suspensions, 24 h after UV‐B exposure. In general, conidia mixed with soil and exposed to UV‐B yielded similar number of colony forming units as conidia from unexposed soil, regardless the soil type. It was not possible to predict which type of propagule would be the most UV‐B tolerant for each fungal isolate; in conclusion, many formulations and propagule types should be investigated early in the development of new fungal biocontrol products. [ABSTRACT FROM AUTHOR]