Genes That Influence Swarming Motility and Biofilm Formation in Variovorax paradoxus EPS

Variovorax paradoxus is an aerobic soil bacterium associated with important biodegradative processes in nature. We use V. paradoxus EPS to study multicellular behaviors on surfaces.We recovered flanking sequence from 123 clones in a Tn5 mutant library, with insertions in 29 different genes, selected based on observed surface behavior phenotypes. We identified three genes, Varpa_4665, Varpa_4680, and Varpa_5900, for further examination. These genes were cloned into pBBR1MCS2 and used to complement the insertion mutants. We also analyzed expression of Varpa_4680 and Varpa_5900 under different growth conditions by qPCR.The 29 genes we identified had diverse predicted functions, many in exopolysaccharide synthesis. Varpa_4680, the most commonly recovered insertion site, encodes a putative N-acetyl-L-fucosamine transferase similar to WbuB. Expression of this gene in trans complemented the mutant fully. Several unique insertions were identified in Varpa_5900, which is one of three predicted pilY1 homologs in the EPS genome. No insertions in the two other putative pilY1 homologs present in the genome were identified. Expression of Varpa_5900 altered the structure of the wild type swarm, as did disruption of the chromosomal gene. The swarming phenotype was complemented by expression of Varpa_5900 from a plasmid, but biofilm formation was not restored. Both Varpa_4680 and Varpa_5900 transcripts were downregulated in biofilms and upregulated during swarming when compared to log phase culture. We identified a putative two component system (Varpa_4664-4665) encoding a response regulator (shkR) and a sensor histidine kinase (shkS), respectively. Biofilm formation increased and swarming was strongly delayed in the Varpa_4665 (shkS) mutant. Complementation of shkS restored the biofilm phenotype but swarming was still delayed. Expression of shkR in trans suppressed biofilm formation in either genetic background, and partially restored swarming in the mutant.The data presented here point to complex regulation of these surface behaviors

Evaluating Variance Control, Order Review/Release & Dispatching: A Regression Analysis

The challenge of improving performance in the job shop can be met in a number of ways. We can rely on variance control to reduce variances created either in the planning system (through uneven or fluctuating loads) or on the shop floor (through varying processing times for released batches). We can rely on Order Review/Release (ORR). Finally, we can turn to one of the various dispatching rules that are available. Each option has been previously examined. However, this study examines all of these options simultaneously within the context of a simulated simple job shop. Based on a regression analysis of the data generated, several interesting results are uncovered. First, the results show that the presence of variance control at both the planning and shop floor levels can greatly enhance the effectiveness of ORR. This result partially helps resolve the controversy surrounding ORR. Second, the results show that Shortest Processing Time (SPT), while extremely effective in an uncontrolled environment, reacts adversely to the presence of variance control. Finally, if used effectively, variance control can greatly reduce the need for complex dispatching rule