Bacterial swarming is a type of motility characterized by a rapid and collective migration of bacteria on surfaces. Most swarming species form densely packed dynamic clusters in the form of whirls and jets, in which hundreds of rod-shaped rigid cells move in circular and straight patterns, respectively. Recent studies have suggested that short-range steric interactions may dominate hydrodynamic interactions and that geometrical factors, such as a cell's aspect ratio, play an important role in bacterial swarming. Typically, the aspect ratio for most swarming species is only up to 5, and a detailed understanding of the role of much larger aspect ratios remains an open challenge. Here we study the dynamics of Paenibacillus dendritiformis C morphotype, a very long, hyperflagellated, straight (rigid), rod-shaped bacterium with an aspect ratio of ϳ20. We find that instead of swarming in whirls and jets as observed in most species, including the shorter T morphotype of P. dendritiformis, the C morphotype moves in densely packed straight but thin long lines. Within these lines, all bacteria show periodic reversals, with a typical reversal time of 20 s, which is independent of their neighbors, the initial nutrient level, agar rigidity, surfactant addition, humidity level, temperature, nutrient chemotaxis, oxygen level, illumination intensity or gradient, and cell length. The evolutionary advantage of this unique back-and-forth surface translocation remains unclear. Motile bacteria are able to colonize surfaces using various motility mechanisms (1). One efficient method includes flagellation-based cell motion in conjunction with collective lubrication (typically by secretion of surfactants) to enable fast expansion on hard surfaces. This mode of "bacterial swarming" that has been studied extensively for many species (1-15) enables rapid colony expansion (up to centimeters per hour). Swarming is often marked by hundreds of cells moving in a coordinated fashion while generating whirl and jet patterns.Studies of the collective dynamics of swarming have examined multiple aspects of motility. On the macroscopic level, it was discovered that swarming colonies show an advantage over liquid cultures in that they exhibit an increased resistance to antimicrobials (1,4,5,(15)(16)(17)(18)(19)(20). Studies of collective secretions of signaling and quorum-sensing molecules have shown how interactions between cells in swarming colonies are controlled (11) and exposed the identification of associated genetic manipulations and upregulated proteins that control biosurfactant secretions and flagellar behavior. On the single-cell level, attention was given to swarm cell trajectories and the ways in which these trajectories are determined by flagellar motion (8,(21)(22)(23). A combination of experiments (2, 3, 14, 15, 24-38) and theory (39-43) suggests that hydrodynamic interactions play a significant role in this social form of migration.Hydrodynamic interactions may not always be the dominant physical mechanism controlling bacterial motion....

No abstract

Background Adequate surgical training is paramount to produce competent surgeons to address the global burden of surgical disease. The Pan‐African Academy of Christian Surgeons (PAACS) has general surgery training programs in eight countries. Operative case volumes have been positively associated with improved trainee performance and patient outcomes. For certification in the USA, 850 total operations are required from defined case categories. Yet, little is known about the operative experience of surgical trainees throughout Africa. Methods Operative procedures were reviewed, categorized, and validated from a cohort of PAACS graduates and compared to graduates from Accreditation Council for Graduate Medical Education (ACGME) programs. The primary and secondary outcomes were total case volumes and cases within ACGME‐defined categories. Regional variations were explored. Results Twenty PAACS trainees, from five programs in four countries, performed 38,267 unique procedures. ACGME reports on 1211 residents from 251 programs. PAACS graduates logged more major cases (median 1448) than ACGME graduates (median 993) (p value = 0·0001). PAACS graduates performed more gynecology and obstetrics, orthopedics, head and neck, urology, endocrine, operative trauma, pediatric surgery, plastic surgery, and skin and soft tissue cases. US graduates performed more cases in abdomen, alimentary tract, breast, thoracic, and vascular categories. Comparison between regions demonstrated volume and category variations between Kenya and Gabon, Ethiopia, and Cameroon. Conclusion PAACS trainees perform more operations than ACGME trainees with differences in distribution. This experience can serve as a model for regional educational programs seeking to address the broad and largely unmet burden of surgical disease.

Background Resident operative case volumes are an important aspect of surgical education, and minimums are required in Accreditation Council for Graduate Medical Education (ACGME) programs. Minimum operative case volumes for training do not exist in rural Africa. Our objective was to determine the optimal minimum operative case volume necessary for general surgery training in rural Africa. Methods A cross‐sectional census electronic survey was conducted among faculty (N = 24) and graduates (N = 56) of Pan‐African Academy of Christian Surgeons training programs. Three equally weighted exposures (median minimum case volume suggested by participants, operative experience of prior graduates, and comparisons with ACGME minimums), adjusted from responses to targeted questions, were utilized to construct an optimal minimum operative case volume for training. Results Sixty‐four surgeons were contacted and 40 (13 faculty, 24 graduates, and 3 graduates who became faculty) participated. All participants thought operative case minimums were necessary, and the majority (98%) felt current training adequately prepared surgeons for their setting. Constructed optimal case volumes included 1000 major cases with fewer required cases than ACGME in abdomen, breast, thoracic, vascular, endoscopy, and laparoscopy and more required cases than ACGME for alimentary tract, endocrine, operative trauma, skin and soft tissue, pediatric, and plastic surgery. Other categories (gynecology, orthopedics, and urology) were deemed necessary for surgical training, with regional differences. Prior graduates satisfied the overall, but not category‐specific, proposed minimums. Conclusions The surveyed surgeons highlighted the need for diverse surgical training with minimum exposures. They described increased need for cases reflecting regional variations with a desire for more experience in categories less common at their institutions.

Rationale 2‐Hydroxyglutarate (2‐hg) exists as enantiomers and can readily undergo cyclization to its lactone. Gas chromatography/electron ionization mass spectrometry (GC/EI‐MS) has been used to separate 2‐hg enantiomers in bodily fluids but the assay cannot simultaneously measure cyclic and acylic 2‐hg enantiomers. Furthermore, the assignment of ion structures was not verified by complementary MS data. Methods GC/EI‐MS and product ion analysis were used to obtain MS and MS/MS spectra of 2‐hg, deuterated and 13C‐labeled 2‐hg, and 2‐hg lactone. Ion structures and EI fragmentation mechanisms were determined by fragmentation pattern and isotopologue comparisons. Using the EI data, a GC/MS/MS assay was developed to separate and detect 2‐hg enantiomers and 2‐hg lactone enantiomers in blood and urine using a cyclodextrin capillary column. Results A new ion structure was predicted for the 85 m/z fragment than what was previously hypothesized, and the 117 m/z ion was the only fragment unique to the linear 2‐hg compound. MS/MS data suggested that the majority of the fragments were the result of secondary fragmentation. Finally, separation of serum and urine 2‐hg and 2‐hg lactone enantiomers was achieved, and the acyclic 2‐hg compound was found to be the major compound detected, though the amount of lactone detected was considerable in a number of samples. Conclusions Unique EI fragmentation pathways for both 2‐hg and the 2‐hg lactone have been described. Subsequently, the GC/MS/MS assay presented herein has significant potential as a novel clinical assay as it separates and detects both 2‐hg enantiomers and the 2‐hg lactone enantiomers, a capability which has not been previously demonstrated by any other assay to date.