A microsporidian impairs Plasmodium falciparum transmission in Anopheles arabiensis mosquitoes

A possible malaria control approach involves the dissemination in mosquitoes of inherited symbiotic microbes to block Plasmodium transmission. However, in the Anopheles gambiae complex, the primary African vectors of malaria, there are limited reports of inherited symbionts that impair transmission. We show that a vertically transmitted microsporidian symbiont (Microsporidia MB) in the An. gambiae complex can impair Plasmodium transmission. Microsporidia MB is present at moderate prevalence in geographically dispersed populations of An. arabiensis in Kenya, localized to the mosquito midgut and ovaries, and is not associated with significant reductions in adult host fecundity or survival. Field-collected Microsporidia MB infected An. arabiensis tested negative for P. falciparum gametocytes and, on experimental infection with P. falciparum, sporozoites aren’t detected in Microsporidia MB infected mosquitoes. As a microbe that impairs Plasmodium transmission that is non-virulent and vertically transmitted, Microsporidia MB could be investigated as a strategy to limit malaria transmission

Genomic survey of the non-cultivatable opportunistic human pathogen, Enterocytozoon bieneusi

© 2009 The Authors. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in PLoS Pathogens 5 (2009): e1000261, doi:10.1371/journal.ppat.1000261.Enterocytozoon bieneusi is the most common microsporidian associated with human disease, particularly in the immunocompromised population. In the setting of HIV infection, it is associated with diarrhea and wasting syndrome. Like all microsporidia, E. bieneusi is an obligate, intracellular parasite, but unlike others, it is in direct contact with the host cell cytoplasm. Studies of E. bieneusi have been greatly limited due to the absence of genomic data and lack of a robust cultivation system. Here, we present the first large-scale genomic dataset for E. bieneusi. Approximately 3.86 Mb of unique sequence was generated by paired end Sanger sequencing, representing about 64% of the estimated 6 Mb genome. A total of 3,804 genes were identified in E. bieneusi, of which 1,702 encode proteins with assigned functions. Of these, 653 are homologs of Encephalitozoon cuniculi proteins. Only one E. bieneusi protein with assigned function had no E. cuniculi homolog. The shared proteins were, in general, evenly distributed among the functional categories, with the exception of a dearth of genes encoding proteins associated with pathways for fatty acid and core carbon metabolism. Short intergenic regions, high gene density, and shortened protein-coding sequences were observed in the E. bieneusi genome, all traits consistent with genomic compaction. Our findings suggest that E. bieneusi is a likely model for extreme genome reduction and host dependence.This research was supported by National Institutes of Health (NIH) grants R21 AI064118 (DEA) and R21 AI52792 (ST). HGM was supported in part by NIH contracts HHSN266200400041C and HHSN2662004037C (Bioinformatics Resource Centers) and by the G. Unger Vetlesen Foundation

The digestion of protein and carbohydrate by the stream detritivore, Tipula abdominalis (Diptera, Tipulidae)

The digestive system of larvae of Tipula abdominalis (Diptera, Tipulidae), a stream detritivore, is poorly adapted for the digestion of the major polysaccharides in its diet, but well adapted for the digestion of protein. These crane fly larvae are unable to digest the major cell wall polysaccharides of higher plants, i.e., cellulose, hemicellulose and pectin. The only polysaccharides toward which the midguts of T. abdominalis exhibited any activity were α-amylose and laminarin, indicating that polysaccharide digestion is restricted to α-1,4-and β-1,3-glucans. The most concentrated source of these two classes of carbohydrates in submerged leaf litter would be associated fungal tissue. The midgut of T. abdominalis is strongly alkaline throughout, with a maximum pH near 11.5 in a narrow zone near the midpoint. Proteolytic activity in the midgut is extraordinarily high, and the pH optimum for midgut proteolytic activity is above 11. We conclude that the high alkalinity and high proteolytic activity observed in T. abdominalis larvae are manifestations of a highly efficient protein-digesting system, a system of crucial importance to a nitrogen-limited organism which must derive its nitrogen from a resource in which much of the limited nitrogen present is in a “bound” form in complexes of proteins with lignins and polyphenols.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47733/1/442_2004_Article_BF00346265.pd

Microsporidiosis of Tachinaephagus zealandicus Ashmead (Hymenoptera: Encyrtidae)

An undescribed microsporidium was found infecting Tachinaephagus zealandicus, a gregarious parasitoid that attacks third instar larvae of muscoid flies. Spores were present in all body regions and in all stages of development. Infected adults contained an average of 3.75 x 10(5) spores, and the pathogen was vertically transmitted to progeny. Infected female adults were fed either rifampicin or albendazole mixed with honey to determine the effectiveness of these drugs in preventing vertical transmission. After eight days of feeding on rifampicin the parasitoids produced progeny of which only 37% were infected. In contrast, albendazole-treated and untreated females produced progeny that were 97% and 100% infected, respectively. Healthy and infected colonies were established and studies were conducted to determine the mechanisms of transmission. It was observed that the efficiency of vertical (maternal) transmission was 96.3%. Uninfected parasitoid immatures also became infected when they shared superparasitized hosts with infected immatures. The method of transmission within superparasitized hosts is not known