Encarnacion Martinez-Salas, Margarita Saiz and Francisco Sobrino

Foot-and-mouth disease virus (FMDV) is the prototypic member of the Aphthovirus genus in the Picornaviridae family. This picornavirus is the etiological agent of an acute systemic vesicular disease that affects cattle worldwide. Here we have addressed several aspects dealing with the molecular biology of this highly variable and transmissible virus that are relevant to understand the viral infectious cycle. Particular emphasis has been given to the peculiarities of its genome organization, as well as its control of gene expression. Soon after infection, the single stranded positive RNA that constitutes the viral genome is efficiently translated using a cap-independent mechanism driven by the internal ribosome entry site element (IRES). This process occurs concomitantly with the inhibition of cellular protein synthesis, caused by the expression of viral proteases. Processing of the viral polyprotein is achieved cotranslationally by viral encoded proteases, giving rise to the different mature viral proteins. Viral RNA as well as viral proteins interact with different components of the host cell, acting as key determinants of viral pathogenesis. In depth knowledge of the molecular basis of the viral cycle is needed to control viral pathogenesis and disease spreading.

More information from: "Foot-and-Mouth Disease Virus" Chapter 1 in Animal Viruses: Molecular Biology

Patrick Eichenberger

Bacteria of the genera Bacillus and Clostridium can be found in two distinct states. In the vegetative state, the bacterium is metabolically active and uses available nutrients to grow and divide by binary fission, a process that generates two identical daughter cells. By contrast, when nutrients are scarce, a developmental program of endospore formation (sporulation) is initiated, resulting in the production of a highly resistant spore. In the spore state, the bacterium is metabolically dormant, and its genetic material, protected in the core of the spore, can endure a variety of challenges, including radiation, heat and chemicals. Sporulation is a complex process, which requires the generation of two distinct cell types: a forespore and a larger mother cell. The progression of the developmental program is controlled by two exquisitely regulated cell type-specific lines of gene expression that run in parallel and are connected at the post-transcriptional level. Various genetic screens and genome-wide transcriptional analyses have identified more than 600 genes that are expressed in the course of sporulation. The function of several of these genes has been characterized in detail and subcellular localization data are available for more than 70 sporulation proteins. Thus, sporulation constitutes one of the best characterized developmental programs at the molecular and cellular levels.

More information from: "Genomics and Cellular Biology of Endospore Formation" Chapter 11 in Bacillus: Cellular and Molecular Biology