34 research outputs found
Microbiological evaluation of different antiseptic povidone-iodine and chlorhexidine formulations after intentional contamination of containers
Novel Methods for Analysing Bacterial Tracks Reveal Persistence in Rhodobacter sphaeroides
Tracking bacteria using video microscopy is a powerful experimental approach to probe their motile behaviour. The
trajectories obtained contain much information relating to the complex patterns of bacterial motility. However, methods for
the quantitative analysis of such data are limited. Most swimming bacteria move in approximately straight lines,
interspersed with random reorientation phases. It is therefore necessary to segment observed tracks into swimming and
reorientation phases to extract useful statistics. We present novel robust analysis tools to discern these two phases in tracks.
Our methods comprise a simple and effective protocol for removing spurious tracks from tracking datasets, followed by
analysis based on a two-state hidden Markov model, taking advantage of the availability of mutant strains that exhibit
swimming-only or reorientating-only motion to generate an empirical prior distribution. Using simulated tracks with varying
levels of added noise, we validate our methods and compare them with an existing heuristic method. To our knowledge this
is the first example of a systematic assessment of analysis methods in this field. The new methods are substantially more
robust to noise and introduce less systematic bias than the heuristic method. We apply our methods to tracks obtained
from the bacterial species Rhodobacter sphaeroides and Escherichia coli. Our results demonstrate that R. sphaeroides exhibits
persistence over the course of a tumbling event, which is a novel result with important implications in the study of this and
similar species
Fast-Moving Bacteria Self-Organize into Active Two-Dimensional Crystals of Rotating Cells
Analysis of aerotactic band formation by Desulfovibrio desulfuricans in a stopped-flow diffusion chamber
Bacterial growth and motility in sub-micron constrictions
In many naturally occurring habitats, bacteria live in micrometer-size confined spaces. Although bacterial growth and motility in such constrictions is of great interest to fields as varied as soil microbiology, water purification, and biomedical research, quantitative studies of the effects of confinement on bacteria have been limited. Here, we establish how Gram-negative Escherichia coli and Gram-positive Bacillus subtilis bacteria can grow, move, and penetrate very narrow constrictions with a size comparable to or even smaller than their diameter. We show that peritrichously flagellated E. coli and B. subtilis are still motile in microfabricated channels where the width of the channel exceeds their diameters only marginally (∼30%). For smaller widths, the motility vanishes but bacteria can still pass through these channels by growth and division. We observe E. coli, but not B. subtilis, to penetrate channels with a width that is smaller than their diameter by a factor of approximately 2. Within these channels, bacteria are considerably squeezed but they still grow and divide. After exiting the channels, E. coli bacteria obtain a variety of anomalous cell shapes. Our results reveal that sub-micron size pores and cavities are unexpectedly prolific bacterial habitats where bacteria exhibit morphological adaptations