Adaptation of Borrelia burgdorferi to its natural hosts by synonymous codon and amino acid usage.

Lyme disease, caused by Borrelia burgdorferi, is a focally endemic tick-transmitted zoonotic infection. In this study, the major factors underlying synonymous codon-related amino acid usage in the B. burgdorferi genome and bias in synonymous codon usage of the translation initiation region of coding sequences were analyzed. Additionally, adaptation of B. burgdorferi to several of its hosts was analyzed in the context of synonymous codon usage. Principal component analysis (PCA) revealed that nucleotide content at the third synonymous position of a codon influenced the synonymous codon usage pattern, but the strand-specific factor did not influence the synonymous codon usage pattern of B. burgdorferi. In terms of the low GC content of B. burgdorferi coding sequences, the effective number of codons (ENC) showed a significant correlation with GC3 content (at the synonymous position). For the amino acid usage pattern for B. burgdorferi, PCA showed that the strand-specific factor did not contribute to this pattern, while the properties (aromaticity and hydrophobicity) of the amino acids themselves showed strong correlations with this pattern. Under-represented codons, which were frequently selected in the translation initiation region, possibly play roles in regulating gene expression in B. burgdorferi. In terms of co-evolution and synonymous codon usage patterns, adaptation of B. burgdorferi to different intermediate hosts was apparent to different degrees, and the degree of adaptation of this spirochete to wild animals was stronger than that of humans or mice.

In Vitro, in Vivo, and Interaction Studies of Nematophagous Fungus Arthrobotrys thaumasia ( Monacrosporium thaumasium) with the Larvae of Trichostrongylides of Sheep.

It is important to isolate potential candidates from the local isolates of nematophagous fungi and to investigate interaction between the fungal strains and gastrointestinal nematodes for the biological control of parasitic nematodes in livestock. In the present study, we assessed the in vitro predatory activity and the viability of isolates of Arthrobotrys thaumasia ( Monacrosporium thaumasium) after passage through the gastrointestinal tract of sheep. The predatory process of a representative isolate selected against the larvae of trichostrongylids was prepared with a scanning electron microscope (SEM). In vitro experiments tested the ability of 9 native isolates of A. thaumasia to prey on larvae of feces of sheep infected with natural mixed nematodes ( Haemonchus contortus, Trichostongylus colubriformis, Marshallagia mongolica). These isolates of A. thaumasia decreased infectivity of third stage infective larvae (L3) by 75.54-99.97%; 7 isolates decreased infectivity by more than 90%. In vivo experiments also demonstrated significant reductions of L3 numbers in the feces treated with the 9 isolates after passing through the gastrointestinal tract of sheep, and these decreases ranged from 51.68 to 88.16%. The isolates tested were re-isolated in 5-g sub-samples of feces from sheep in each treatment group, indicating that these isolates had the capacity to prey upon larvae of trichostrongylids after the passage through gastrointestinal tract. SEM shows that at 6 hr after the larvae were added, including the second stage larvae (L2) and L3 of trichostrongylids, the isolate NBS 005 caught them; at 8 hr after being caught L2 was penetrated by the fungus while penetration of L3 occurred at 12 hr; at 78 hr post-capture L2 was completely destroyed by the fungus while complete digestion of L3 occurred at 84 hr.