Flagellar point mutation causes social aggregation in laboratory-adapted Bacillus subtilis under conditions that promote swimming.

Motility allows microbes to explore and maximize success in their environment; however, many laboratory bacterial strains have a reduced or altered capacity for motility. Swimming motility in Bacillus subtilis depends on peritrichous flagella and is carried out individually as cells move by biased random walks toward attractants. Previously, we adapted Bacillus subtilis strain 3610 to the laboratory for 300 generations in lysogeny broth (LB) batch culture and isolated lab-adapted strains. Strain SH2 is motility-defective and in broth culture forms large, frequently spherical aggregates of cells. A single point mutation in the flagellin gene hag that causes amino acid 259 to switch from A to T is necessary and sufficient to cause these social cell aggregates, and aggregation occurs between flagellated cells bearing this point mutation regardless of the strain background. Cells associate when bearing this mutation, but flagellar rotation is needed to pull associating cells into spherical aggregates. Using electron microscopy, we are able to show that the SH2 flagellar filament has limited polymorphism when compared to other flagellar structures. This limited polymorphism hinders the flagellum's ability to function as a motility apparatus but appears to alter its function to that of cell aggregation/adhesion. We speculate that the genotype-specific aggregation of cells producing HagA259T flagella could have increased representation in a batch-culture experiment by allowing similar cells to go through a transfer together and also that this mutation could serve as an early step to evolve sociality in the natural world.IMPORTANCEThe first life forms on this planet were prokaryotic, and the earliest environments were aquatic, and from these relatively simple starting conditions, complex communities of microbes and ultimately multicellular organisms were able to evolve. Usually, motile cells in aqueous environments swim as individuals but become social by giving up motility and secreting extracellular substances to become a biofilm. Here, we identify a single point mutation in the flagellum that is sufficient to allow cells containing this mutation to specifically form large, suspended groups of cells. The specific change in the flagellar filament protein subunits causes a unique change in the flagellar structure. This could represent a distinct way for closely related cells to associate as an early precursor to sociality.

Rapid sequence intubation medication therapies: a review in light of recent drug shortages.

Rapid sequence intubation is a stepwise process developed to assist health care providers in placing emergent artificial airways for patients requiring assisted ventilation. This practice includes routine administration of sedative and neuromuscular blocking agent (NMBA) medications for patient comfort during endotracheal tube placement. Members of the multidisciplinary team should be well educated about the various medications used during this process to ensure safe medication practices in an emergent situation. Recent drug shortages have forced many health care professionals to use alternative medications with which they are less familiar. The intent of this review is to familiarize health care providers with the pharmacology and adverse effect profiles of alternative sedative and NMBA medications used in emergent airway placement in light of recent drug shortages.

Review of vasopressor therapy in the setting of vasodilatory shock.

Appropriate selection and utilization of vasopressor therapy are important in the treatment of vasodilatory shock, because inappropriate use can result in increased morbidity and mortality. Vasopressors are differentiated on the basis of their receptor activity, as well as their pharmacokinetic and pharmacodynamic properties. Understanding the pathophysiology of receptor responses in shock, dose-dependent receptor activity variations, and unique patient-specific factors that alter response, all assist the health care provider in selecting the appropriate agent for each patient. Treatment is further individualized on the basis of clinical response and medication titration, as well as laboratory value changes. The intent of this review is to discuss relevant management issues associated with vasopressor use in the emergency department.

Evaluation of morbidity and mortality data related to cardiovascular calcification from calcium-containing phosphate binder use in patients undergoing hemodialysis.

Cardiovascular disease is the leading cause of death among patients with stage 5 chronic kidney disease. Several mechanisms are thought to contribute to vascular calcification and subsequent cardiovascular disease in patients who require hemodialysis. One of these mechanisms is the use of calcium-containing phosphate binders to treat hyperphosphatemia. Although most phosphate binding occurs in the gastrointestinal tract, some calcium is inevitably absorbed and has the potential to perpetuate the calcium-phosphorus product and the development of vascular and soft tissue calcification. Some phosphate binders such as sevelamer hydrochloride do not contain calcium and therefore may not carry the same risks. We examined the cardiovascular calcification effect and morbidity and mortality data with calcium-containing phosphate binders compared with sevelamer hydrochloride when given to patients with stage 5 chronic kidney disease for the treatment of hyperphosphatemia. A literature search using the MEDLINE and PubMed databases identified relevant articles from 1989-2009; nine studies compared vascular calcification between a calcium-containing phosphate binder and sevelamer hydrochloride. Three mortality studies were also identified. Seven of the nine studies reported a statistically significant increase in vascular calcification in patients taking calcium-containing phosphate binders as measured by coronary artery calcification scores and aortic calcification scores. In two trials, lower mortality rates were observed in the patients receiving sevelamer hydrochloride compared with calcium-containing phosphate binders. No significant difference in the mortality rate was observed in the third trial. Based on the current literature, it appears that calcium-containing phosphate binders promote the progression of vascular calcification to a greater extent than does sevelamer hydrochloride. In addition, some evidence suggests that sevelamer hydrochloride may reduce all-cause mortality rates in patients undergoing hemodialysis, particularly those aged 65 years or older. Thus, although sevelamer hydrochloride appears to be the more appropriate choice of phosphate binder for patients undergoing hemodialysis in whom cardiovascular calcification is a concern, more clinical trials are needed to further guide practitioners on the selection of phosphate binders.