Rend Lake College

Antimicrobial peptides (AMPs) are found widely as part of nonspecific immune defenses. One class of AMPs forms stable pores in membranes, including the two chemically distinct membranes found in the Gram-negative cell envelope. As the Gram-negative cell envelope is a significant barrier to drug development, some have hypothesized that these AMPs could be used clinically, either alone or in combination with other drugs that cannot cross the Gram-negative cell envelope on their own. Here, we use atomic force microscopy (AFM), fluorescence spectroscopy, and fluorescence microscopy to elucidate the biomechanical changes that occur in Escherichia coli treated with various concentrations of the pore-forming AMP magainin 2 (MAG2). We find that near the minimum inhibitory concentration, MAG2 induces a loss of cell stiffness and a decrease in cell height consistent with pore formation and cellular leakage. Surprisingly, treatment with high concentrations of MAG2 leads to cells becoming stiffer and increasing in height. We confirmed that MAG2 forms pores at high concentrations using a standard propidium iodide (PI) uptake assay, in which PI is added to a cell suspension and is detected only after pores form in the cell membrane. However, when PI was added after 30 min of treatment with high concentrations of MAG2, less PI fluorescence was observed than in the standard PI uptake assay, indicating that movement across the cell membrane was restricted at the end of our experiments. We also observed that the modulus of the cell envelope increased with increasing MAG2 concentration, consistent with greater packing of MAG2 into the cell envelope membranes. Finally, our AFM images in air revealed that cells formed blebs when treated with high concentrations of MAG2. These data suggest that MAG2 initially forms pores at high concentrations, but as membrane packing increases, movement across the cell envelope becomes restricted. Understanding the concentration-dependent restriction of movement across the cell envelope could be important if AMPs are to be used clinically.

Robbing and bartering is a habitual behavior among free-ranging long-tailed macaques (Macaca fascicularis) at a single site in Bali, Indonesia. The behavior consists of three main elements: (1) a macaque takes an item from a human; (2) the macaque maintains possession of the item; then (3) the macaque releases or hands off the item after accepting a food offer from a human. In this paper, we analyze data on individual variation in robbing and bartering among subadult males in relation to dominance rank. Using focal animal sampling we collected 197 observation hours of data on 13 subadult males from two groups (6 from Celagi; 7 from Riting) at the Uluwatu temple site from May 2017 to March 2018, recording 44 exchanges of items for food from 92 total robberies following 176 total attempts. We also measured dominance rank using interaction data from our focal animals. Dominance rank was strongly positively correlated with robbery efficiency in Riting, but not Celagi, meaning that more dominant Riting subadult males exhibited fewer overall robbery attempts per successful robbery. We suggest the observed variation in robbing and bartering practices indicates there are crucial, yet still unexplored, social factors at play for individual robbing and bartering decisions.

This article describes the formation and work of a nationwide Qatar Simulation Consortium. In 2013, members included the schools of medicine, nursing, and allied health in Qatar, as well as the public health care system and a private, publicly funded hospital. The mission of the consortium is to foster simulation collaboration among health care and educational institutions and advance simulation education, research, and practice to align with current global standards.