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. 2015 Jul;9(7):1662-76.
doi: 10.1038/ismej.2014.255. Epub 2015 Jan 9.

Similarities and Seasonal Variations in Bacterial Communities From the Blood of Rodents and From Their Flea Vectors

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Similarities and Seasonal Variations in Bacterial Communities From the Blood of Rodents and From Their Flea Vectors

Carmit Cohen et al. ISME J. .
Free PMC article

Abstract

Vector-borne microbes are subject to the ecological constraints of two distinct microenvironments: that in the arthropod vector and that in the blood of its vertebrate host. Because the structure of bacterial communities in these two microenvironments may substantially affect the abundance of vector-borne microbes, it is important to understand the relationship between bacterial communities in both microenvironments and the determinants that shape them. We used pyrosequencing analyses to compare the structure of bacterial communities in Synosternus cleopatrae fleas and in the blood of their Gerbillus andersoni hosts. We also monitored the interindividual and seasonal variability in these bacterial communities by sampling the same individual wild rodents during the spring and again during the summer. We show that the bacterial communities in each sample type (blood, female flea or male flea) had a similar phylotype composition among host individuals, but exhibited seasonal variability that was not directly associated with host characteristics. The structure of bacterial communities in male fleas and in the blood of their rodent hosts was remarkably similar and was dominated by flea-borne Bartonella and Mycoplasma phylotypes. A lower abundance of flea-borne bacteria and the presence of Wolbachia phylotypes distinguished bacterial communities in female fleas from those in male fleas and in rodent blood. These results suggest that the overall abundance of a certain vector-borne microbe is more likely to be determined by the abundance of endosymbiotic bacteria in the vector, abundance of other vector-borne microbes co-occurring in the vector and in the host blood and by seasonal changes, than by host characteristics.

Figures

Figure 1
Figure 1
Mean relative abundance of bacterial genera (that is, sequences classified as a certain genus, as percentage of the total number of sequences) detected in the different sample types (female fleas (FF), male fleas (MF) or rodent blood (B)) collected from 16 female and male G. andersoni hosts. The hosts were trapped either as juveniles (JH) or as adults (AH) during the spring (SP), and resampled as adults at the end of summer (SU). The most abundant genera (that is, those comprising at least 20% of the total sequences in at least one DNA sample) are specified, whereas all remaining sequences are represented as ‘others'. Collective data are shown (a) from all host individuals and (b) for only blood samples. *Only class is provided because the phylotype was not classified to lower taxonomic levels.
Figure 2
Figure 2
Nonmetric multidimensional scaling (MDS) ordination of bacterial communities in female fleas (FF; pink), male fleas (MF; blue) and host blood (B; red). Samples were collected from G. andersoni rodents during the spring (SP; empty circles) or summer (SU; filled circles). MDS is based on Bray–Curtis similarities in fourth root transformed abundance data of the different bacterial phylotypes. Each point represents a bacterial community from each sample, and the proximity between points represents the extent of similarity in bacterial community compositions. One outlier, namely, a bacterial community in a male flea, was omitted.
Figure 3
Figure 3
Mean abundance of Bartonella sp., which were the most abundant and influential bacterial phylotype found, in female fleas (FF; pink), male fleas (MF; blue) and rodent blood (B; red). Samples were collected from G. andersoni hosts, trapped during the spring (SP) and summer (SU). Data from all hosts are combined.
Figure 4
Figure 4
Bacterial phylotype diversity (mean Fisher's α-index) measured for bacterial communities obtained from female fleas, male fleas and host blood samples (FF, MF and B, respectively). Samples were obtained from female (FH) and male (MH) G. andersoni rodent hosts, trapped either as juveniles (JH) or as adults (AH) during the spring (SP), and resampled as adults during the summer (SU). Values below and above the median are indicated by a white and black color, respectively, and values that are more than twice the median are indicated by a gray color. (a) Data of all bacterial communities; (b) data of the bacterial communities excluding the most dominant and influential phylotypes: one Bartonella and two Wolbachia phylotypes.
Figure 5
Figure 5
Comparison of microbiota stability (means±s.e. of the Jaccard index) within and between host individuals.

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