Natural assemblages of marine bacteria exhibiting high-speed motility and large accelerations

Abstract

Natural communities of marine bacteria, an isolate (FMB-Bf3) from one marine community, and Escherichia coli were examined by video microscopy for the magnitude and uniformity of their speed. Natural communities formed tight microswarms that showed higher speeds (mean ‫؍‬ 230 m s ؊1) than did E. coli (15 m s ؊1) or FMB-Bf3 (mean ‫؍‬ 62 m s ؊1). Outside the microswarms, the marine bacteria slowed to 45 m s ؊1. Between turns, in mid run, and while travelling in straight lines, the natural-community bacteria accelerated up to 1,450 m s ؊2 while the cultured bacteria showed maximum accelerations of 70 and 166 m s ؊2. The frequency distribution of speed change for the marine bacteria was skewed towards a few large negative accelerations and a range of positive accelerations. The general pattern was one of relatively slow increases in speed followed by abrupt declines. The results indicate that the mechanical generation and energetic maintenance, as well as the environmental function, of bacterial motility need reappraisal. We conclude that the standard bacterial motility parameters of low and uniform speed, derived from culture-based studies, are not necessarily applicable to marine bacterial communities.

Energy saving mechanisms, collective behavior and the variation range hypothesis in biological systems: A review

“…A prediction that follows from the variation range hypothesis is that when collective speeds are five times maximal individual speeds, as indicated by Mitchell et al (1995), some bacteria among the collective will be smaller in size or maximal metabolic capacity than their larger or stronger counterparts by a corresponding factor of five, bearing in mind appropriate adjustments for the unique fluid dynamics of bacteria, as discussed.…”

“…Indeed, Mitchell et al (1995) identified the unresolved extraordinary efficiencies in energy consumption by which micro-swarming bacteria move in speeds at multiples of the predicted 100 % energetic consumption. These efficiencies imply a set of energy saving mechanisms that are not yet well understood.…”

Modelling and analysis of bacterial tracks suggest an active reorientation mechanism inRhodobacter sphaeroides

“…A related consideration is variation in swimming speeds across individuals. Several studies have noted the highly heterogeneous nature of bacterial populations in terms of swimming speeds [7,39,40]. In our models, we fixed the swimming speed; an obvious extension is to replace this with a fluctuating quantity.…”

Connecting single-cell properties to collective behavior in multiple wild isolates of the Enterobacter cloacae complex

“…Although the difference between swimming and non-swimming cells is not clear, previous studies have reported a few mechanisms of motility regulation in bacteria. Motility in some species is regulated by environmental conditions [42][43][44], and the production of flagella can be regulated by a genetic switch [45]. Non-swimming cells were not stuck to chamber surfaces, as all cells migrated multiple cell lengths during the data acquisition period.…”

“…Although non-swimming cells would contribute to the shape and dynamics of chemotactic gradients, it seems reasonable that non-swimming cells would not strongly influence the band speed. Many studies have shown that fraction of motile bacterial cells is usually low (about 10%) in natural environment, and may vary a lot (5% to 70%) depending on environmental factors [12,42,44,46,47].…”