Current Understanding on Adhesion and Biofilm Development in Actinobacteria.

Biofilm formation and microbial adhesion are two related and complex phenomena. These phenomena are known to play an important role in microbial life and various functions with positive and negative aspects. Actinobacteria have wide distribution in aquatic and terrestrial ecosystems. This phylum is very large and diverse and contains two important genera Streptomyces and Mycobacteria. The genus Streptomyces is the most biotechnologically important, while the genus Mycobacteria contains the pathogenic species of Mycobacteriaceae. According to the literature, the majority of studies carried out on actinomycetes are focused on the detection of new molecules. Despite the well-known diversity and metabolic activities, less attention has been paid to this phylum. Research on adhesion and biofilm formation is not well developed. In the present review, an attempt has been made to review the literature available on the different aspects on biofilm formation and adhesion of Actinobacteria. We focus especially on the genus Streptomyces. Furthermore, a brief overview about the molecules and structures involved in the adhesion phenomenon in the most relevant genus is summarized. We mention the mechanisms of quorum sensing and quorum quenching because of their direct association with biofilm formation.

Relationship between sulfate groups and biological activities of fucans.

The anticoagulant and antiproliferative effects of low molecular weight fucans with different sulfate content were examined. The anticoagulant activity was determined by activated partial thromboplastin time and the antiproliferative one was achieved in vitro on CCL39 fibroblast cell line. The results showed that inhibitory effects of fucans on both coagulation and cell proliferation are dependent on their sulfation degree. Decreased sulfation diminishes the two activities not in the same manner: some low molecular weight fucan fractions with no anticoagulant activity retain their ability to inhibit cell growth.

Antitumor activity of low molecular weight fucans extracted from brown seaweed Ascophyllum nodosum.

The effect of low molecular weight fucans (LMW fucans) has been examined on the proliferation of tumour cells. These LMW fucans are not active on all tumour cell lines. They are not cytotoxic and inhibit CCL39 fibroblast cells and human colon adenocarcinoma Colo320DM proliferation (85% and 50% of inhibition respectively). The active concentration of sulphated polysaccharide is about 10 micrograms/mL for CCL39 cells and 100 micrograms/mL for COLO 320 DM. This inhibitory effect is fetal calf serum concentration and cell density dependent. Furthermore, fucans are internalized into CCL39 cells within the first hours of incubation. They are distributed into the cytoplasmic compartment but not in the nucleus, and are not excreted after one week of contact. In the case of COLO 320 DM cells, the same fluorescent fucan is not internalized after one week of contact, but remains strongly fixed on the cytoplasmic membrane. This inhibitory effect is not accompanied by any modifications of the cell distribution in the various phases of the cell cycle. There are no significant differences in the antitumor effect either between the various LMW fucan or with the crude extract.

Affinity of trypsin for amidine derivatives immobilized on dextran-coated silica supports.

The pancreas contains two very analogous enzymes: trypsin and chymotrypsin. These two enzymes are very similar in their physicochemical characteristics and are therefore quite difficult to separate by classical purification procedures. They constitute a good model for affinity chromatography. It was previously demonstrated that amidine derivatives are able to interact strongly and specifically with these serine proteases and are often used as ligand in affinity chromatography. To understand the trypsin interaction mechanism, we synthesized different amidines and immobilised them with or without spacer arm on silica beads previously coated by dextran substituted with a calculated amount of positively charged diethylaminoethyl functions, in order to minimize the non-specific interactions of silanol groups of the silica material. First the affinity constant and the adsorption capacity of these supports for trypsin were determined in batch procedures, then they were used in affinity chromatography. The effects of ionic strength, pH and competitive inhibitors on proteins desorption were also studied. Last, to demonstrate the importance of passivation, the chromatographic performances of dextran-coated silica phases and a commercial support grafted with the same amidine were compared.