Inflammation and infection of bovine mammary glands, commonly known as mastitis, imposes significant losses each year in the dairy industry worldwide. While several different bacterial species have been identified as causative agents of mastitis, many clinical mastitis cases remain culture negative, even after enrichment for bacterial growth. To understand the basis for this increasingly common phenomenon, the composition of bacterial communities from milk samples was analyzed using culture independent pyrosequencing of amplicons of 16S ribosomal RNA genes (16S rDNA). Comparisons were made of the microbial community composition of culture negative milk samples from mastitic quarters with that of non-mastitic quarters from the same animals. Genomic DNA from culture-negative clinical and healthy quarter sample pairs was isolated, and amplicon libraries were prepared using indexed primers specific to the V1–V2 region of bacterial 16S rRNA genes and sequenced using the Roche 454 GS FLX with titanium chemistry. Evaluation of the taxonomic composition of these samples revealed significant differences in the microbiota in milk from mastitic and healthy quarters. Statistical analysis identified seven bacterial genera that may be mainly responsible for the observed microbial community differences between mastitic and healthy quarters. Collectively, these results provide evidence that cases of culture negative mastitis can be associated with bacterial species that may be present below culture detection thresholds used here. The application of culture-independent bacterial community profiling represents a powerful approach to understand long-standing questions in animal health and disease.
Bacterial community composition in blood-sucking arthropods can shift dramatically across time and space. We used 16S rRNA gene amplification and pyrosequencing to investigate the relative impact of vertebrate host-related, arthropod-related and environmental factors on bacterial community composition in fleas and ticks collected from rodents in southern Indiana (USA). Bacterial community composition was largely affected by arthropod identity, but not by the rodent host or environmental conditions. Specifically, the arthropod group (fleas vs ticks) determined the community composition of bacteria, where bacterial communities of ticks were less diverse and more dependent on arthropod traits—especially tick species and life stage—than bacterial communities of fleas. Our data suggest that both arthropod life histories and the presence of arthropod-specific endosymbionts may mask the effects of the vertebrate host and its environment.
Diabetes mellitus is a major risk factor for chronic periodontitis. We investigated the effects of type 2 diabetes on the subgingival plaque bacterial composition by applying culture-independent 16S rDNA sequencing to periodontal bacteria isolated from four groups of volunteers: non-diabetic subjects without periodontitis, non-diabetic subjects with periodontitis, type 2 diabetic patients without periodontitis, and type 2 diabetic patients with periodontitis. A total of 71,373 high-quality sequences were produced from the V1-V3 region of 16S rDNA genes by 454 pyrosequencing. Those 16S rDNA sequences were classified into 16 phyla, 27 classes, 48 orders, 85 families, 126 genera, and 1141 species-level OTUs. Comparing periodontally healthy samples with periodontitis samples identified 20 health-associated and 15 periodontitis-associated OTUs. In the subjects with healthy periodontium, the abundances of three genera (Prevotella, Pseudomonas, and Tannerella) and nine OTUs were significantly different between diabetic patients and their non-diabetic counterparts. In the subjects carrying periodontitis, the abundances of three phyla (Actinobacteria, Proteobacteria, and Bacteriodetes), two genera (Actinomyces and Aggregatibacter), and six OTUs were also significantly different between diabetics and non-diabetics. Our results show that type 2 diabetes mellitus could alter the bacterial composition in the subgingival plaque.
Summary1. Many endotherms employ torpor during periods of resource scarcity, but this state of substantially reduced body temperature and metabolism appears to impose significant physiological costs. Accordingly, individuals can be expected to vary the expression of torpor according to the size of their energy reserves. 2. Although dietary polyunsaturated fatty acids (PUFAs) are important for maintaining the fluidity of membrane phospholipids and depot fats at low body temperatures, they are also prone to autoxidation, which can result in significant somatic damage. Dietary PUFA may thus influence the depth and duration of torpor during hibernation. 3. We evaluated the hypothesis that both an increase in the size of the burrow food hoard and an elevation of its PUFA composition can cause chipmunks to reduce their use of torpor both by reducing the time spent torpid and by maintaining higher body temperature during torpor. 4. We provided individual chipmunks with equicaloric natural-PUFA and high-PUFA supplements 10 days prior to autumn immergence. We measured seven parameters that characterize the depth and duration of torpor used by hibernating chipmunks using temperature-sensitive data loggers mounted on neck collars. We compared torpor patterns for the natural-PUFA, high-PUFA and control groups at a study site in southern Quebec, Canada. We also compared control animals from Quebec with unsupplemented controls from a more southerly site in Pennsylvania, USA characterized by higher food availability and less severe winters. 5. Chipmunks provided with natural-PUFA supplements spent less than half as much time in torpor as control animals at the same study site, and when in torpor they exhibited skin temperatures almost twice as high as controls. Chipmunks provided with high-PUFA supplements significantly reduced the depth and duration of torpor bouts compared with animals provided with natural-PUFA supplements. The torpor patterns of unsupplemented chipmunks at the southern site approximated those of natural-PUFA chipmunks at the main study site. 6. Our results provide clear evidence that chipmunks adjust the depth and duration of torpor expression according to both the size and the composition of their energy reserves. Furthermore, both the extent and the nutritional form of environmental energy availability are important determinants of the cost and benefits of torpor expression by free-ranging endotherms.
Torpor is a reversible reduction in endotherm body temperature and metabolic rate. Because torpid endotherms can attain lower body temperatures in colder environments, minimum torpor metabolism generally increases with rising air temperature whereas euthermic metabolism generally declines with rising air temperature. As a result, the fundamental metabolic niche of endotherms that express torpor should be driven by climate and should be broadest in colder environments. On the other hand, if torpor serves primarily as an energy conservation strategy and its expression is influenced by energy availability, then the realized metabolic niche should be defined by resources. To evaluate the influence of resource and climate on torpor use and metabolism of hibernating mammals, we monitored the torpor expression of free-ranging eastern chipmunks (Tamias striatus) over two winters of varying resource abundance. In the low-food year, soil temperature constrained maximum torpor expression but was too invariant across small spatial scales to explain individual variation in torpor expression. In the high-food year, torpor was drastically reduced, and local density of seed-producing trees predicted fine-scale spatial variation in torpor expression. Thus, the fundamental metabolic niche of hibernating chipmunks in cold environments is broad and constrained by climate, whereas the realized metabolic niche is highly variable among individuals and years and is determined primarily by local resource abundance.
Eastern chipmunks ( Tamias striatus (L., 1758)) capitalize on pulsed production of storable seed from masting trees by accumulating large, long-term larder hoards in their burrow. Since this species does not accumulate fat, hoarded food is the sole source of energy used during hibernation and inactive periods. Because hoards can be very large, they offer chipmunks the possibility of forgoing aboveground foraging when seeds or nuts are not abundant on the forest floor. Here, we present evidence that at least 82 chipmunks in two different populations interrupted aboveground activity for 9–11 months when mast was not available. A large hoard of American beech ( Fagus grandifolia Ehrh.) nuts established during the preceding year appeared to allow these chipmunks to cease foraging for almost a full year when food availability was particularly low. This extended period of inactivity is among the longest reported for a hibernating mammal, and demonstrates complex interactions between past, current, and future resource availability in shaping the seasonal activity patterns of food-storing hibernators.
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.
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