High-Throughput Microfluidic Sorting of Live Magnetotactic Bacteria.

Magnetic nanoparticles (MNPs) are useful for many biomedical applications, but it is challenging to synthetically produce them in large numbers with uniform properties and surface functionalization. Magnetotactic bacteria (MTB) produce magnetosomes with homogenous sizes, shapes, and magnetic properties. Consequently, there is interest in using MTB as biological factories for MNP production. Nonetheless, MTB can only be grown to low yields, and wild-type strains produce low numbers of MNPs/bacterium. There are also limited technologies to facilitate the selection of MTB with different magnetic contents, such as MTB with compromised and enhanced biomineralization ability. Here, we describe a magnetic microfluidic platform combined with transient cold/alkaline treatment to temporarily reduce the rapid flagellar motion of MTB without compromising their long-term proliferation and biomineralization ability for separating MTB on the basis of their magnetic contents. This strategy enables live MTB to be enriched, which, to the best of our knowledge, has not been achieved with another previously described magnetic microfluidic device that makes use of ferrofluid and heat. Our device also facilitates the high-throughput (25,000 cells/min) separation of wild-type Magnetospirillum gryphiswaldense (MSR-1) from nonmagnetic ΔmamAB MSR-1 mutants with a sensitivity of up to 80% and isolation purity of up to 95%, as confirmed with a gold-standard fluorescent-activated cell sorter (FACS) technique. This offers a 25-fold higher throughput than other previously described magnetic microfluidic platforms (1,000 cells/min). The device can also be used to isolate Magnetospirillum magneticum (AMB-1) mutants with different ranges of magnetosome numbers with efficiencies close to theoretical estimates. We believe this technology will facilitate the magnetic characterization of genetically engineered MTB for a variety of applications, including using MTB for large-scale, controlled MNP production.IMPORTANCE Our magnetic microfluidic technology can greatly facilitate biological applications with magnetotactic bacteria, from selection and screening to analysis. This technology will be of interest to microbiologists, chemists, and bioengineers who are interested in the biomineralization and selection of magnetotactic bacteria (MTB) for applications such as directed evolution and magnetogenetics.

Adult attention deficit hyperactivity disorder and other psychiatric symptoms in recreational polydrug users.

AIMS: Previous research has shown that recreational drug use is associated with more psychiatric symptoms and psychobiological distress. This study investigated whether symptoms of adult attention deficit hyperactivity disorder (ADHD) were also raised in polydrug users. METHODS: We assessed a non-clinical sample of 84 unpaid volunteers (mean age 27.5 years): n = 17 light-novice polydrug users; n = 29 moderate polydrug users; and n = 38 non-user controls (14 non-drug users, 24 alcohol/tobacco users). They completed the Symptom Checklist 90 (SCL-90) self-rating inventory for psychiatric symptoms, the Adult ADHD Self-report Scale symptom checklist for adult ADHD, and also the questions on positive moods and sociability. Saliva samples provided a neuroendocrine cortisol measure. RESULTS: Moderate polydrug users reported significantly higher adult ADHD symptoms and SCL-90 psychiatric symptoms and lower sociability than non-user controls and light polydrug users. Novice-light polydrug users did not differ from control groups on any measure. There were no significant group differences in cortisol. These findings are debated using the interactive diathesis-distress model. Psychoactive drugs can affect both mood and cognition. When taken regularly, the drug-induced psychobiological vacillation may exacerbate prior problems with mood stability and attentional-cognitive control. CONCLUSIONS: It is not polydrug usage per se, but rather their regular-repeated usage, that is associated with increased signs of psychiatric and attentional-hyperactivity distress.