The bacterial biofilm is a microbial community in which bacteria are embedded in the extracellular matrix and can also be used as a solid composite. It was found that internal stresses are generated during pellicle growth, which exists between the air and the liquid. But we do not know if there is the internal stress in the biofilm, which exists between the air and the solid, and how does the internal stress evolve and distribute in the growing biofilm. So, in this paper, we make the growing substrate into the micropillar array to grow biofilms, each micropillar has the deformation due to the growing heterogeneity of the biofilm around the micropillar, and we can get the internal stress by measuring each micropillar’s deformation. First, we find that the direction of the internal stress is approximately along the biofilm expansion at the early time, colonies are formed in the biofilm at the later time, which cause the internal stress locally along the expansion of the colony. Second, the internal stress is proportional to the biofilm thickness. Finally, we find that the matrix producing cells contribute more the internal stress, and the internal stress evolving is closely related to the secretion of the extracellular matrix. Form our work, we obtain the distribution of the internal stress direction, we also can use the biofilm thickness, which is easy to measure, express the internal stress approximately, by doing so, we can further study other phenomena of biofilms, such as self-healing and mechanical resistance.
Genetic recombination plays an important role in shaping the within-species genetic variations. It has been generally accepted that current-day population evolved from a small number of specific sequences called founders, and the genomic sequences (called recombinants) of individuals within the population are composed of segments from the founders due to recombination. A related computational problem is the so-called Minimum Founder Set problem: construct the minimum founder set from a set of given recombinant sequences so that the minimum fragment length is not less than the given fragment length bound. Ukkonen presented a segmentation based dynamic programming (SDYN) algorithm to solve it. However, the number of reconstructed founders obtained by the SDYN algorithm is restricted by the given fragment length bound in a certain situation. In this paper, a practical constructive heuristic algorithm HMFS is proposed for solving the problem. The HMFS algorithm partitions the sites of founders into three parts and reconstructs them respectively. Experimental results show that the HMFS algorithm can reconstruct a founder set very quickly, and the solutions obtained by the HMFS algorithm are close to or better than those obtained by the SDYN algorithm. In addition, the HMFS algorithm runs much faster than the SDYN algorithm, it is still efficient for solving large size problems.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.