Phyllobacterium Calauticae Sp. Nov. Isolated From a Microaerophilic Veil Transversed by Cable Bacteria in Freshwater Sediment

Microaerophilic veils of swimming microorganisms form at oxic-anoxic interfaces, most commonly described in sediments where sulfide diffusing out from below meets oxygen diffusing in from the water phase. However, distinctive microaerophilic veils form even when there is a gap between the sulfide and O2 fronts, i.e., a suboxic zone, and suggest that the organisms inhabiting these veils can use electron donors other than sulfide. Suboxic zones are found for example in sediment where cable bacteria spatially separate sulfide and O2 by up to several centimetres. Here we describe the extraction of microorganisms from a microaerophilic veil that formed in cable-bacteria-enriched freshwater sediment using a glass capillary, and the subsequent isolation of a motile, microaerophilic, organoheterotrophic bacterium, strain R2-JLT, unable to oxidize sulfide. Based on phenotypic, phylogenetic, and genomic comparison, we propose strain R2-JLT as a novel Phyllobacterium species, P. calauticae sp. nov.. The type strain is R2-JLT (=LMG 32286T =DSM 112555T). This novel isolate confirms that a wider variety of electron donors, including organic compounds, can fuel the activity of microorganisms in microaerophilic veils.

Bioinspired reorientation strategies for application in micro/nanorobotic control

Engineers have recently been inspired by swimming methodologies of microorganisms in creating micro-/nanorobots for biomedical applications. Future medicine may be revolutionized by the application of these small machines in diagnosing, monitoring, and treating diseases. Studies over the past decade have often concentrated on propulsion generation. However, there are many other challenges to address before the practical use of robots at the micro-/nanoscale. The control and reorientation ability of such robots remain as some of these challenges. This paper reviews the strategies of swimming microorganisms for reorientation, including tumbling, reverse and flick, direction control of helical-path swimmers, by speed modulation, using complex flagella, and the help of mastigonemes. Then, inspired by direction change in microorganisms, methods for orientation control for microrobots and possible directions for future studies are discussed. Further, the effects of solid boundaries on the swimming trajectories of microorganisms and microrobots are examined. In addition to propulsion systems for artificial microswimmers, swimming microorganisms are promising sources of control methodologies at the micro-/nanoscale.