Three-Dimensional Culture of Rhipicephalus (Boophilus) microplus BmVIII-SCC Cells on Multiple Synthetic Scaffold Systems and in Rotating Bioreactors

Tick cell culture facilitates research on the biology of ticks and their role as vectors of pathogens that affect humans, domestic animals, and wildlife. Because two-dimensional cell culture doesn’t promote the development of multicellular tissue-like composites, we hypothesized that culturing tick cells in a three-dimensional (3-D) configuration would form spheroids or tissue-like organoids. In this study, the cell line BmVIII-SCC obtained from the cattle fever tick, Rhipicephalus (Boophilus) microplus (Canestrini, 1888), was cultured in different synthetic scaffold systems. Growth of the tick cells on macrogelatinous beads in rotating continuous culture system bioreactors enabled cellular attachment, organization, and development into spheroid-like aggregates, with evidence of tight cellular junctions between adjacent cells and secretion of an extracellular matrix. At least three cell morphologies were identified within the aggregates: fibroblast-like cells, small endothelial-like cells, and larger cells exhibiting multiple cytoplasmic endosomes and granular vesicles. These observations suggest that BmVIII-SCC cells adapted to 3-D culture retain pluripotency. Additional studies involving genomic analyses are needed to determine if BmVIII-SCC cells in 3-D culture mimic tick organs. Applications of 3-D culture to cattle fever tick research are discussed.

Environmental fluctuations reshape an unexpected diversity-disturbance relationship in a microbial community

SummaryEnvironmental disturbances have long been theorized to play a significant role in shaping the diversity and composition of ecosystems1,2. However, fundamental limitations in our ability to specify the characteristics of a disturbance in the field and laboratory have produced an inconsistent picture of diversity-disturbance relationships (DDRs) that shape the structure of ecosystems3. Here, using a recently developed continuous culture system with tunable environmental control4, we decomposed a dilution disturbance into intensity and fluctuation components5,6, and tested their effects on the diversity of a soil-derived bacterial community across hundreds of replicate cultures. We observed an unexpected U-shaped relationship between community diversity and disturbance intensity in the absence of fluctuations, an observation counter to classical intuition. Adding fluctuations erased the U-shape and increased community diversity across all disturbance intensities. All of these results are well-captured by a Monod consumer resource model, which further reveals how U-shaped DDRs emerge based on a novel “niche flip” mechanism in which competitive outcomes flip and coexistence regimes subsequently collapse at intermediate disturbance levels. Broadly, our results demonstrate how distinct features of an environmental disturbance can interact in complex ways to govern ecosystem assembly and produce all the major classes of DDRs, without invoking other organizational principles. With these findings, we construct a unifying framework that reconciles the disparate DDRs observed in nature, and propose strategies for predictively reshaping the compositional complexity of microbiomes and other ecosystems.