Upon termination of translation, the fate of ribosomes is determined largely by the rate at which cells are growing. During periods of exponential growth, ribosomes are rapidly recycled, translation is re-initiated, and the ribosomes are extremely stable. However, when nutrient sources become limiting, and ribosomes are not actively translating, they may become substrates for degradation. While this phenomenon is well known, details of how the process is initiated and what are the signals for degradation have, until now, remained elusive. Here, I present in vitro and in vivo data showing that free ribosome subunits are the targets of degradative enzymes, whereas 70S particles that remain associated are protected from such degradation. Conditions that increase the formation of subunits both in vitro and in vivo lead to enhanced degradation. Thus, the simple presence of free 50S and 30S subunits is sufficient to serve as the mechanism that initiates ribosome degradation. In order to identify RNases involved in ribosome degradation, both in vitro and in vivo assays were developed. Together, they have provided evidence for a multi-step degradation process involving both endo- and exoribonucleases. Examination of extracts from strains deficient in known RNases revealed that the endoribonucleases, RNase E and RNase G, may be involved in the initial cleavages. The resulting fragments, some of which are small enough oligoribonucleotides that they remain part of the acid-soluble fraction are degraded to mononucleotides primarily by the 3'-5' exoribonucleases, RNase R and polynucleotide phosphorylase.

Microbial enzymes implicated in plant cell hydrolysis may have several potential aplications such as biomass degradation biocatalysts or with biofuel production. Bark beetles establish symbiosis with several microbial strains which play different roles benifitting the beetle, as the production of hydrolytic enzymes to degrade the ingested wood, the protection against mirobial antagonist or the detoxification of the environment. Fungal symbionts have been traditionally the best studied, but several recent research with bacterial symbionts of several bark beetle species show that bacterial also display important functions for the host. In this study, the bacterial communities of the bark beetle species Cryphalus piceae and Pithophtorus pithophtorus, collected in the Czech Republic from pine and fir trees, respectively, were isolated and 55 out of 89 samples were identified by 16S rRNA gene amplification and sequencing. Members of the genera Erwinia, Pantoea, Curtobacterium, Yersinia, Pseudomonas and Staphylococcus were detected. The isolates were object of study for their possible biotechnological potential in (ligno)cellulose materials degradation by screening several enzymes implicated in plant cell hydrolysis, as cellulases, xylanases, amylases, laccases, as well as their capability for colorant...