Enzymatic degradation of abundant renewable polysaccharides such as cellulose and starch is a field that has the attention of both the industrial and scientific community. Most of the polysaccharide degrading enzymes are classified into several glycoside hydrolase families. They are often organized in a modular manner which includes a catalytic domain connected to one or more carbohydrate-binding modules. The carbohydrate-binding modules (CBM) have been shown to increase the proximity of the enzyme to its substrate, especially for insoluble substrates. Therefore, these modules are considered to enhance enzymatic hydrolysis. These properties have played an important role in many biotechnological applications with the aim to improve the efficiency of polysaccharide degradation. The domain organization of glycoside hydrolases (GHs) equipped with one or more CBM does vary within organisms. This review comprehensively highlights the presence of CBM as ancillary modules and explores the diversity of GHs carrying one or more of these modules that actively act either on cellulose or starch. Special emphasis is given to the cellulase and amylase distribution within the filamentous microorganisms from the genera of Streptomyces and Aspergillus that are well known to have a great capacity for secreting a wide range of these polysaccharide degrading enzyme. The potential of the CBM and other ancillary domains for the design of improved polysaccharide decomposing enzymes is discussed.

Manganese is oxidized by a wide variety of bacteria. The current state of knowledge on mechanisms and functions of Mn²⁺ oxidation in two strains of Pseudomonas putida, in Leptothrix discophora SS-1, and in Bacillus sp. strain SG-1 is reviewed. In all three species, proteins bearing resemblance to multicopper oxidases appear to be involved in the oxidation process. A short description of the classification of Cu centers is followed by a more detailed review of properties and postulated functions of some well-known multicopper oxidases. Finally, suggestions are made for future research to assess the potential role of multicopper oxidases in bacterial Mn²⁺ oxidation.

Filamentous actinomycetes are commercially widely used as producers of natural products (in particular antibiotics) and of industrial enzymes. However, the mycelial lifestyle of actinomycetes, resulting in highly viscous broths and unfavorable pellet formation, has been a major bottleneck in their commercialization. Here we describe the successful morphological engineering of industrially important streptomycetes through controlled expression of the morphogene ssgA . This led to improved growth of many industrial and reference streptomycetes, with fragmentation of the mycelial clumps resulting in significantly enhanced growth rates in batch fermentations of Streptomyces coelicolor and Streptomyces lividans . Product formation was also stimulated, with a twofold increase in yield of enzyme production by S. lividans . We anticipate that the use of the presented methodology will make actinomycetes significantly more attractive as industrial and sustainable production hosts.

In Escherichia coli transcription of the tRNA operon thrU (tufB) and the rRNA operon rrnB is trans-activated by the protein FIS. This protein, which stimulates the inversion of various viral DNA segments, binds specifically to a cis-acting sequence (designated UAS) upstream of the promoter of thrU (tufB) and the P1 promoter of the rrnB operon. There are indications that this type of regulation is representative for the regulation of more stable RNA operons. In the present investigation we have studied UAS-dependent transcription activation of the thrU (tufB) operon in the presence and absence of FIS during a normal bacterial growth cycle and after a nutritional shift-up. In early log phase the expression of the operon rises steeply in wild-type cells, whereafter it declines. Concomitantly, a peak of the cellular FIS concentration is observed. Cells in the stationary phase are depleted of FIS. The rather abrupt increase of transcription activation depends on the nutritional quality of the medium. It is not seen in minimal medium. After a shift from minimal to rich medium, a peak of transcription activation and of FIS concentration is measured. This peak gets higher as the medium gets more strongly enriched. We conclude that a correlation between changes of the UAS-dependent activation of the thrU (tufB) operon and changes of the cellular FIS concentration under a variety of experimental conditions exists. This correlation strongly suggests that the production of FIS responds to environmental signals, thereby trans-activating the operon. Cells unable to produce FIS (fis cells) also show an increase of operon transcription in the early log phase and after a nutritional shift-up, albeit less pronounced than that wild-type cells. Presumably it is controlled by the ribosome feedback regulatory system. cis activation of the operon by the upstream activator sequence is apparent in the absence of FIS. This activation is constant throughout the entire growth cycle and is independent of nutritional factors. The well-known growth rate-dependent control, displayed by exponentially growing cells studied under various nutritional conditions, is governed by two regulatory mechanisms: repression, presumably by ribosome feedback inhibition, and stimulation by trans activation. FIS allows very fast bacterial growth.

Summary: The role of the blue copper protein azurin and cytochrome C₅₅₁ as the possible electron donors to nitrite reductase in the dissimilatory nitrate reduction pathway in Pseudomonas aeruginosa have been investigated. It was shown by an in vivo approach with mutant strains of P. aeruginosa deficient in one or both of these electron-transfer proteins that cytochrome C₅₅₁, but not azurin, is functional in this pathway. Expression studies demonstrated the presence of azurin in both aerobic and anaerobic cultures. A sharp increase in azurin expression was observed when cultures were shifted from exponential to stationary phase. The stationary-phase sigma factor, σ^s, was shown to be responsible for this induction. In addition, one of the two promoters transcribing the azu gene was regulated by the anaerobic transcriptional regulator ANR. An azurin-deficient mutant was more sensitive to hydrogen peroxide and paraquat than the wild-type P. aeruginosa. These results suggest a physiological role of azurin in stress situations like those encountered in the transition to the stationary phase.