Influence of temperature preferences of two Paecilomyces fumosoroseus lineages on their co-infection pattern

Bacterial and viral co-infections in aquaculture under climate warming: co-evolutionary implications, diagnosis, and treatment

Climate change and the associated environmental temperature fluctuations are contributing to increases in the frequency and severity of disease outbreaks in both wild and farmed aquatic species. This has a significant impact on biodiversity and also puts global food production systems, such as aquaculture, at risk. Most infections are the result of complex interactions between multiple pathogens, and understanding these interactions and their co-evolutionary mechanisms is crucial for developing effective diagnosis and control strategies. In this review, we discuss current knowledge on bacteria-bacteria, virus-virus, and bacterial and viral co-infections in aquaculture as well as their co-evolution in the context of global warming. We also propose a framework and different novel methods (e.g. advanced molecular tools such as digital PCR and next-generation sequencing) to (1) precisely identify overlooked co-infections, (2) gain an understanding of the co-infection dynamics and mechanisms by knowing species interactions, and (3) facilitate the development multi-pathogen preventive measures such as polyvalent vaccines. As aquaculture disease outbreaks are forecasted to increase both due to the intensification of practices to meet the protein demand of the increasing global population and as a result of global warming, understanding and treating co-infections in aquatic species has important implications for global food security and the economy.

The Virtuous Galleria mellonella Model for Scientific Experimentation

The first research on the insect Galleria mellonella was published 85 years ago, and the larva is now widely used as a model to study infections caused by bacterial and fungal pathogens, for screening new antimicrobials, to study the adjacent immune response in co-infections or in host-pathogen interaction, as well as in a toxicity model. The immune system of the G. mellonella model shows remarkable similarities with mammals. Furthermore, results from G. mellonella correlate positively with mammalian models and with other invertebrate models. Unlike other invertebrate models, G. mellonella can withstand temperatures of 37 °C, and its handling and experimental procedures are simpler. Despite having some disadvantages, G. mellonella is a virtuous in vivo model to be used in preclinical studies, as an intermediate model between in vitro and mammalian in vivo studies, and is a great example on how to apply the bioethics principle of the 3Rs (Replacement, Reduction, and Refinement) in animal experimentation. This review aims to discuss the progress of the G. mellonella model, highlighting the key aspects of its use, including experimental design considerations and the necessity to standardize them. A different score in the "cocoon" category included in the G. mellonella Health Index Scoring System is also proposed.

Susceptibility of All Nymphal Stages of Bemisia tabaci Biotype B (Hemiptera: Aleyrodidae) to Three Brazilian Isolates of Cordyceps sp. (Hypocreales: Cordycipitaceae) in a Screenhouse Under Variable Temperature and Moisture Conditions

The susceptibility of 1st to 4th instars of Bemisia tabaci (Gennadius, 1989) (Hemiptera: Aleyrodidae) to three isolates of Cordyceps sp. (Hypocreales: Cordycipitaceae) was evaluated in screenhouse experiments under variable temperatures and moisture conditions. No differences in susceptibility to the Cordyceps sp. isolates were observed among 1st, 2nd, and 3rd instar nymphs with respect to median lethal time (LT₅₀) values. Confirmed mortalities ranged from 63.7 to 87.8% when the isolates were tested at 5 × 10⁷ conidia mL^-1. The 4th instar was the least susceptible to the fungal isolates (≤ 36.6% mortality). However, 60.0 to 99.5% of the adults that emerged from 4th instar nymphs previously treated with the fungus succumbed to the infection. Temperature was more detrimental to Cordyceps sp. virulence towards B. tabaci nymphs than relative humidity (RH). At similar RH, median LT₅₀ for 1st instar (9.4 days) was higher than for 3rd instar (5.3 days) when the fungus was tested at 5 × 10⁷ conidia mL^-1; minimal temperatures of ≥ 12.6°C compared to ≥ 17.0°C were registered for experiments with 1st and 3rd instars, respectively. However, temperatures ≥ 35°C for 4 to 6 h daily did not affect the efficacy of the fungus against nymphs. Cordyceps sp. showed high virulence to all life stages of B. tabaci at relatively low RH, and an ability to grow extensively over the leaf surface and to produce high amounts of conidia on infected hosts. These attributes certainly boost its potential as an important pest control component of B. tabaci biotype B, especially for management of populations resistant to synthetic insecticides.

Selection of a fungal isolate for the control of the pink hibiscus mealybug Maconellicoccus hirsutus

BACKGROUND

Maconellicoccus hirsutus Green is a widely distributed pest of numerous crops. Although synthetic pesticides are used to control this pest, entomopathogenic fungi may provide an alternative control mechanism. Three experiments were carried out to select a fungal isolate with the potential to be used as a microbial control agent. The in vitro growth of five isolates of Beauveria bassiana sensu lato (Bals.) Vuill and Metarhizium anisopliae sensu lato (Metschn.) Sorokín, along with three isolates of Lecanicillium lecanii (Zimm.) Zare & W. Gams and Isaria fumosoroseus (Wize), was assessed at four temperatures. The in vivo sporulation of eight selected isolates was then evaluated, followed by the susceptibility of third-instar M. hirsutus to a single dose (1 × 10(8) conidia mL(-1) ) of each of these isolates.

RESULTS

Growth was greatest by isolates of I. fumosoroseus and L. lecanii at 15 and 20 °C and by isolates of M. anisopliae at 25 and 30 °C. In vivo conidium production was greatest when infected with B. bassiana isolate GHA and M. anisopliae isolate Ma65. Mortality was greatest when inoculated with M. anisopliae isolates Ma65 and Ma129.

CONCLUSION

Isolate Ma65 shows the best potential to be developed as a microbial control agent for M. hirsutus.

Performance of two isolates of Isaria fumosorosea from hot climate zones in solid and submerged cultures and thermotolerance of their propagules

Isaria fumosorosea frequently causes mycosis of agricultural pests in the hot semiarid and dry tropical regions of Mexico. Because temperature tolerance restricts the use of fungal biopesticides, we investigated two isolates from these areas for possible development into mycoinsecticides for use in hot weather agricultural zones. We studied the effects of culture system (solid or submerged cultures) and temperature on the fungal growth, extracellular enzyme production, pathogenicity, and thermotolerance of the produced propagules. Between 20 and 28 °C, the specific growth rates of the isolate PCC were higher on solid media, but in the submerged culture, the isolate P43A grew faster even at temperatures of up to 34 °C. On solid media, P43A produced 1.5-fold more proteases than PCC, but in the submerged culture, both strains had similar activities. Under the same culture conditions, PCC produced a blastospore:conidia ratio of 1:2, and P43A produced a ratio of 1:5. PCC aerial conidia had the shortest Lethal Time 50 (LT(50), the time to reach 50 % mortality) against Galleria mellonella larvae, but LT(50) was equal for the aerial conidia and the submerged propagules of P43A and PCC. The submerged and aerial propagules of P43A were more thermotolerant than those of PCC. Each isolate performed differently in each culture system, and we concluded that the intended production method should be included as a criterion for screening of entomopathogenic fungus. We found that thermotolerance is a specific characteristic of an isolate from a given species. Because of its specific characteristics, P43A shows more promise for the development of a submerged conidia-based mycoinsecticide for foliar application in aqueous form in hot climate regions.

Effects of temperature and culture media on vegetative growth of an entomopathogenic fungus Isaria sp. (Hypocreales: Clavicipitaceae) naturally affecting the whitefly, Bemisia tabaci in Texas

The effects of temperature and mycological media on mycelial growth and estimates of spore production of an indigenous entomopathogenic fungus, Isaria sp., found during natural epizootics on whiteflies in the Lower Rio Grande Valley of Texas, were investigated. The radial growth (mm/day) of Isaria sp. as a function of temperature fits a linear model; with faster growth on Sabouraud dextrose agar with yeast extract, SDAY slopes (0.23) than on Sabouraud maltose agar, SMA slopes (0.14) from 20 to 30 degrees C, with an optimal temperature of 30 degrees C (SDAY: 4.1 mm, SMA: 3.1 mm). Moderate growth occurred at 25 degrees C (SDAY: 3.4 mm, SMA: 2.7 mm). Growth was lowest at 20 degrees C (SDAY: 1.9 mm, SMA: 1.8 mm). No fungal growth was observed at 35 degrees C and 40 degrees C. However, when Isaria sp. was exposed to 35 degrees C for the first 7 days, it could recover and grow when transferred to 25 degrees C (SDAY: 3.5 mm, SMA: 2.8 mm). No recovery or growth occurred after transfer from 40 degrees C to 25 degrees C. The average conidial production on SDAY after 20 days incubation at 25 degrees C and a photoperiod of 14:10 h light: dark was 1.2 x 10(8) conidia/cm(2) with 100% spore viability. When compared on SDAY at 25 degrees C, the radial growth rate of I. javanica ex type CBS 134.22 (5.1 mm/day) was greater than seven Isaria isolates including Isaria sp.; but maximum growth rates were similar among all related Isaria isolates (90-97%). The Isaria sp. fungus tolerates high temperatures (35 degrees C), suggesting that it is naturally selected for the subtropical semi-arid environment, where it could serve as an important natural control agent of the sweet potato whitefly, Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) biotype B, one of the most invasive and economically damaging insects to agriculture.

Environmental and behavioral constraints on the infection of wireworms by Metarhizium anisopliae

Environmental and behavioral factors that affect the infection of wireworms [Agriotes obscurus L. (Coleoptera: Elateridae)] by a unique isolate of Metarhizium anisopliae Sorokin (Hypocreales: Clavicipitaceae) were studied. After wireworms were placed in soil containing 10(6) M. anisopliae conidia/g and incubated at 6, 12, or 18 degrees C, significant disease development and wireworm mortality occurred only in those wireworms incubated at 18 degrees C. At this temperature, mortality was found to be dependant on the time exposed to the contaminated soil, and a minimum exposure time of 48 h was required to cause significant levels of mortality. Despite the restrictive effect of cooler temperatures on disease development and mortality, infected wireworms did not choose temperatures that inhibited disease development when given the opportunity to do so in a separate experiment. Finally, wireworms were repelled by M. anisopliae-contaminated soil at a rate that increased with the soil conidia concentration, but the rate of emigration was reduced when a food source was present. The results of this study indicate that factors including temperature, time exposed to M. anisopliae, conidia soil concentration, and food availability will affect mortality rates of wireworms and are likely to affect field performance of M. anisopliae as a biological control.