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The cosmopolitan mosquito Aedes aegypti is a vector of harmful arboviruses. Pyrethroid insecticides are used to reduce adult populations and prevent the spread of disease. Pyrethroids target the insect voltage-gated sodium channel (VGSC). Collectively, mutations in Vgsc that confer resistance are referred to as knock-down resistance or kdr. There are numerous kdr mutations found in A. aegypti Vgsc, and there is co-occurrence of some mutations. Full-length cDNA sequences have identified nine known kdr (e.g., 1534C) alleles. The 1534C allele is among the most common kdr alleles, but allele frequencies between populations vary considerably. We used the 1534C:RK strain, which has the 1534C (kdr) allele in the genetic background of the insecticide susceptible Rockefeller (ROCK) strain, and conducted population cage experiments to assess the potential intrinsic fitness cost of the 1534C allele relative to the susceptible allele (F1534) in the ROCK strain. Individuals were genotyped across generations using allele specific PCR. A fitness cost of the 1534C allele was detected across seven generations of mosquitos reared in the absence of insecticide selection pressure. The decrease in allele frequency was not due to drift. Comparison of our results to previous studies suggests that the magnitude of the fitness cost of kdr alleles in the absence of insecticide is disconnected from the level of resistance they confer, and that the fitness costs of different kdr alleles can be variable.

By the end of the century tens of gigatonnes of CO2 will need to be removed from the atmosphere every year to maintain global temperatures. Natural weathering of ultramafic rocks and subsequent mineralization reactions can convert atmospheric CO2 into ultra-stable carbonates. But, while natural weathering will eventually draw down all excess CO2, this process will need hundreds of thousands of years to do it. The CO2 mineralization process could be accelerated by weathering ultramafic rocks with biodegradable lixiviants like organic acids. But, in this article we show that if these lixiviants are produced from cellulosic biomass, the demand created by CO2 mineralization could monopolize the world's supply of biomass even if CO2 mineralization performance is high. In this article we demonstrate that electromicrobial production technologies that (EMP) combine renewable electricity and microbial metabolism could produce lixiviants for as little as $200 to $400 per tonne at solar electricity prices achievable within the decade. Furthermore, this allows the lixiviants needed to sequester a tonne of CO2 to produced for less than $100, even with modest CO2 mineralization performance.

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