Necrotrophism Is a Quorum-Sensing-Regulated Lifestyle in Bacillus thuringiensis

How pathogenic bacteria infect and kill their host is currently widely investigated. In comparison, the fate of pathogens after the death of their host receives less attention. We studied Bacillus thuringiensis (Bt) infection of an insect host, and show that NprR, a quorum sensor, is active after death of the insect and allows Bt to survive in the cadavers as vegetative cells. Transcriptomic analysis revealed that NprR regulates at least 41 genes, including many encoding degradative enzymes or proteins involved in the synthesis of a nonribosomal peptide named kurstakin. These degradative enzymes are essential in vitro to degrade several substrates and are specifically expressed after host death suggesting that Bt has an active necrotrophic lifestyle in the cadaver. We show that kurstakin is essential for Bt survival during necrotrophic development. It is required for swarming mobility and biofilm formation, presumably through a pore forming activity. A nprR deficient mutant does not develop necrotrophically and does not sporulate efficiently in the cadaver. We report that necrotrophism is a highly regulated mechanism essential for the Bt infectious cycle, contributing to spore spreading

White-Rot Fungi in Bioremediation

Bioremediation is defined as the application of biological processes to the treatment of pollution. Most research on the field of bioremediation has focused on bacteria, and fungal bioremediation (mycoremediation) has also been attracting the interest just for a couple of decades. The toxicity of many pollutants reduces natural attenuation of bacteria, but white-rot fungi (WRF) can challenge with toxic levels of the most pollutants. Fungi are robust organisms having very high tolerance to toxic environments, and this feature makes them ideal to use for bioremedial purposes. White-rot fungi are basidiomycetes that are capable of degrading a lignocellulose substrate. Extracellular enzymes involved in the degradation of lignin and xenobiotics by white-rot fungi include several kinds of laccases, peroxidases, and oxidases producing H2O2. Nowadays, great progress in this area may derive from modern molecular technologies, which may provide cheaper potential sources of various enzymes by means of genetically modified microorganisms or plants. This chapter explains the bioremediation and its application conditions and degradation mechanisms of the harmful compounds such as textile dyes, PAHs, chlorophenols, TNT, pesticides, and nylon