Legionella pneumophila survives and replicates inside host cells by secreting ~300 effectors through the Dot/Icm type IVB secretion system (T4BSS). Here, we used complementary electron cryotomography (ECT) and immunofluorescence microscopy (IF) to investigate the molecular architecture and biogenesis of the Dot/Icm secretion apparatus. ECT mapped the location of the core and accessory components of the Legionella core-transmembrane subcomplex revealing a well-ordered central channel that opens into a large, windowed secretion chamber with an unusual 13-fold symmetry. IF deciphered an early-stage assembly process that begins with targeting of Dot/Icm components to the bacterial poles. Polar targeting of this T4BSS is mediated by two Dot/Icm proteins, DotU and IcmF, that interestingly are homologs of the T6SS membrane complex components TssL and TssM, suggesting the Dot/Icm T4BSS is a hybrid system. Together these results revealed that the Dot/Icm complex assembles in an “axial-to-peripheral” pattern.

Integrative computational modeling is currently the method of choice for studying the detailed mesoscale molecular structure of cellular environments. However, current methods are highly compute intensive and require extensive and diverse domain knowledge. We have developed an interactive mesoscale illustration method, cellPAINT, that allows non-expert users to create mesoscale models that integrate a variety of biological data. CellPAINT uses the approach of popular digital painting software, providing users with a palette of “brushes” to paint molecules and infrastructure into a mesoscale scene, and coloring tools and visual filters to customize the rendering. CellPAINT also incorporates a variety of mesoscale properties, such as an interactive temperature slider that controls diffusive motion and interaction of proteins within membranes. The current release allows creation of scenes with an HIV virion, blood plasma, and a simplified T-cell.

Paenibacillus larvae is a pathogen of honeybees that causes American foulbrood (AFB). We isolated bacteriophages from soil containing bee debris collected near beehives in Utah. We announce five high-quality complete genome sequences, which represent the first completed genome sequences submitted to GenBank for any P. larvae bacteriophage.

Structural molecular biology is now becoming part of high school science curriculum thus posing a challenge for teachers who need to convey three dimensional (3D) structures with conventional text and pictures. In many cases even interactive computer graphics does not go far enough to address these challenges. We have developed a flexible model of the polypeptide backbone using 3D printing technology. With this model we have produced a polypeptide assembly kit to create an idealized model of the Triosephosphate isomerase mutase enzyme (TIM), which forms a structure known as TIM barrel. This kit has been used in a laboratory practical where students perform a step-by-step investigation into the nature of protein folding, starting with the handedness of amino acids to the formation of secondary and tertiary structure. Based on the classroom evidence we collected, we conclude that these models are valuable and inexpensive resource for teaching structural molecular biology.

CellPAINT is an interactive digital tool that allows non-expert users to create illustrations of the molecular structure of cells and viruses. We present a new release with several key enhancements, including the ability to generate custom ingredients from structure information in the Protein Data Bank, and interaction, grouping, and locking functions that streamline the creation of assemblies and illustration of large, complex scenes. An example of CellPAINT as a tool for hypothesis generation in the interpretation of cryoelectron tomograms is presented. CellPAINT is freely available at http://ccsb.scripps.edu/cellpaint.