Culturing Aerobic and Anaerobic Bacteria and Mammalian Cells with a Microfluidic Differential Oxygenator

In this manuscript, we report on the culture of anaerobic and aerobic species within a disposable multilayer polydimethylsiloxane (PDMS) microfluidic device with an integrated differential oxygenator. A gas-filled microchannel network functioning as an oxygen−nitrogen mixer generates differential oxygen concentration. By controlling the relative flow rate of the oxygen and nitrogen input gases, the dissolved oxygen (DO) concentration in proximal microchannels filled with culture media are precisely regulated by molecular diffusion. Sensors consisting of an oxygen-sensitive dye embedded in the fluid channels permit dynamic fluorescence-based monitoring of the DO concentration using low-cost light-emitting diodes. To demonstrate the general utility of the platform for both aerobic and anaerobic culture, three bacteria with differential oxygen requirements (E. coli, A. viscosus, and F. nucleatum), as well as a model mammalian cell line (murine embryonic fibroblast cells (3T3)), were cultured. Growth characteristics of the selected species were analyzed as a function of eight discrete DO concentrations, ranging from 0 ppm (anaerobic) to 42 ppm (fully saturated)

Immobilization of Pseudomonas sp. strain ADP: a stable inoculant for the bioremediation of atrazine

Storage and delivery of beneficial microorganisms are fundamental issues determining their value and effectiveness for a wide range of industrial and environmental purposes. One such application is the use of bacteria for the remediation of soil pollutants such as polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and persistent pesticides. Liquid cultures of a candidate for atrazine degradation in soil and water, Pseudomonas sp. strain ADP (3.67 × 109 colony-forming units, cfu/mL), when stored at 4 and 25 °C, showed a 1 log reduction in cfu/mL occurs after approximately 4 and 2 weeks, respectively. When immobilized onto natural zeolite from two sources (a New Zealand and an Australian quarry) and stored in open containers exposed to the atmosphere, survival at 25 °C was poor. However, when the cells were immobilized onto the Australian zeolite with xanthan gum and stored in closed containers, survival at 25 °C was superior to control cells stored at 4 °C. The initial growth medium, zeolite substratum and immobilization matrix excipients all appear to play an important role in the stabilization of Pseudomonas sp. strain ADP. The bacteria immobilized onto Australian zeolite with xanthan remained viable within 1 log unit of initial cfu/g loading and retained their ability to degrade atrazine (as measured by zone clearance on atrazine containing plates) for at least 10 weeks at 25 °C

Draft genome sequences of two New Zealand Xanthomonas campestris pv. campestris isolates, ICMP 4013 and ICMP 21080

Xanthomonas campestris pv. campestris is a necrotrophic bacterial pathogen of crucifers. We report here the draft genome sequences of isolates ICMP 4013 and ICMP 21080 from New Zealand. These sequences will facilitate the identification of race-specific factors in X. campestris pv. campestris

Inactivation of the gene encoding the cationic antimicrobial peptide resistance factor MprF increases biofilm formation but reduces invasiveness of Listeria monocytogenes

Aims To understand the genetics involved in surface attachment and biofilm formation ofListeria monocytogenes. Methods and Results Anin vitroscreen of a Himar1 transposon library ofL. monocytogenesstrain 15G01 identified three transposants that produced significantly different biofilm levels when compared to the wild-type strain; two mutants exhibited enhanced biofilm formation and one produced less biofilm biomass than the wild-type. The mutant 15G01mprF::Himar1, which had a transposon insertion in themprFgene, was selected for further analysis. The mutant produced a more densely populated biofilm on solid surfaces such as stainless steel and polystyrene, as determined using scanning electron and light microscopy. The 15G01mprF::Himar1 mutant remained viable in biofilms, but showed an increase in sensitivity to the cationic antimicrobial gallidermin. The mutant also displayed reduced invasiveness in CaCo-2 intestinal cells, suggesting virulence properties are compromised by the inactivation ofmprF. Conclusions Biofilm formation and gallidermin resistance ofL. monocytogenesis influenced bymprF, but this trait is associated with a compromise in invasiveness. Significance and Impact of the Study The presence of pathogenic microorganisms in the food processing environment can cause a significant problem, especially when these microorganisms are established as biofilms. This study shows that the inactivation of themprFgene results in enhanced biofilm formation and abiotic surface attachment ofL. monocytogenes.Peer reviewe

Optimized sub-40 nm planar patterning process for a La0.7Sr0.3MnO3 magnetic memory

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