A keystone Methylobacterium strain in biofilm formation in drinking water

The structure of biofilms in drinking water systems is influenced by the interplay between biological and physical processes. Bacterial aggregates in bulk fluid are important in seeding biofilm formation on surfaces. In simple pure and co-cultures, certain bacteria, including Methylobacterium, are implicated in the formation of aggregates. However, it is unclear whether they help to form aggregates in complex mixed bacterial communities. Furthermore, different flow regimes could affect the formation and destination of aggregates. In this study, real drinking water mixed microbial communities were inoculated with the Methylobacterium strain DSM 18358. The propensity of Methylobacterium to promote aggregation was monitored under both stagnant and flow conditions. Under stagnant conditions, Methylobacterium enhanced bacterial aggregation even when it was inoculated in drinking water at 1% relative abundance. Laminar and turbulent flows were developed in a rotating annular reactor. Methylobacterium was found to promote a higher degree of aggregation in turbulent than laminar flow. Finally, fluorescence in situ hybridisation images revealed that Methylobacterium aggregates had distinct spatial structures under the different flow conditions. Overall, Methylobacterium was found to be a key strain in the formation of aggregates in bulk water and subsequently in the formation of biofilms on surfaces

Memory Capacity in a System of Swelling Particles

A system has the ability to store memory if one is able to write, retrieve, and erase information from it. Some systems are capable of storing multiple transient memories; with no noise in these systems, at long time, the memories degrade until one or two remain. The addition of noise to these systems can extend the retention of multiple memories, in some cases indefinitely [2, 3]. While this behavior was first observed in simulations of charge density waves, it has since appeared in other systems [1]. Past research has shown that sheared non-Brownian liquid suspensions of particles exhibit similar behavior with regards to multiple memory storage with noise [2, 3, 5]. In these systems, a memory of the driving shear that a system has been trained with can be written. Training consists of many cycles of driving at a given strain amplitude γ. After training, there is a sharp increase in irreversibility observed for shearing with a strain amplitude of γ ′ \u3e γ [2]. As a result, we can say that the system has formed a memory at γ. In order to write multiple memories in a system, multiple amplitudes are used for the training in some predetermined pattern along with noise. Suppose we intended to train a system with two memories, γ1 and γ2 where γ1 \u3e γ2. In order to train the system to have memories at both amplitudes we may repeat a pattern such as γ1, γ2, γ2, γ2, γ2. The system is sheared to each amplitude successively, with noise applied between each shear, and then the pattern repeats. After sufficient repetitions of this pattern, multiple memories are detectable and persist at long time [3, 4]. While so far we’ve focused on sheared systems, past research by Keim, Paulsen, and Nagel indicates that multiple transient memory behavior is not sensitive to the deformation geometry of the system; for example, a system of swelling particles exhibits similar behavior [3]. This is the type of system used in this study. In this case, training the system is not done by shearing the suspension of particles to a given amplitude or pattern of amplitudes. Instead, the system is trained by swelling particles to a specified size or repeated pattern of sizes. In these swelling systems, we investigate what system parameters influence memory capacity. Memory capacity can be defined as the total number of memories that can be written, stored, and read within one system at the same time. Many parameters about a given system, e.g. the amount of noise, the interaction strength, and the number of particles, may affect the memory capacity

Attitude determination of the spin-stabilized Project Scanner spacecraft

Attitude determination of spin-stabilized spacecraft using star mapping techniqu

Application of Osteopathic Manipulative Medicine to Ameliorate Sepsis Induced Ileus

Graduate Basi