The status of the species Beijerinckia fluminensis Dobereiner and Ruschel 1958. Request for an Opinion.

In a previous article [Oggerin M., Arahal, D. R., Rubio, V. & Marin, I. (2009). Int J Syst Evol Microbiol 59, 2323-2328], it has been shown that strain Beijerinckia fluminensis UQM 1685(T) and its derived equivalent B. fluminensis CIP 106281(T) do not conform to the description of the type strain of Beijerinckia fluminensis Döbereiner and Ruschel 1958. Indeed, both strains were identified as members of the species Rhizobium radiobacter and exhibited marked phenotypic and genotypic differences with members of the genus Beijerinckia. It was concluded that both strains, and any other equivalents derived from them, do not descend from the nomenclatural type. Since then, our attempts to find older deposits of the type strain, hopefully derived from the original isolate, or other existing strains of Beijerinckia fluminensis that could be proposed as a neotype strain, have been in vain. It is therefore proposed that the Judicial Commission should place the name Beijerinckia fluminensis Döbereiner and Ruschel 1958 on the list of rejected names if a suitable replacement type strain or a neotype cannot be found within two years following the publication of this Request (Rule 18c).

Survival of Beijerinckia sp. microencapsulated in carbohydrates by spray-drying.

The encapsulation of Beijerinckia sp. cell suspension in different wall materials using the spray drying technique was performed. Mat dextrin, dehydrated glucose syrups, gum acacia and modified starch materials were tested. Cell viability assays were carried out before and after drying and during storage of the products. The surface area and characteristics of the encapsulated powders were examined using BET adsorption of N(2) and scanning electron microscopy, respectively. The residual moisture content and water activity of the powders were also determined. The best results were obtained with the dehydrated glucose syrup, which resulted in products with the greatest per cent survival during the drying process and subsequent storage period. The products obtained with the dehydrated glucose syrup showed more uniform microcapsule surfaces at lower A(w) values and residual moisture content.

Activity and survival of spray-dried Beijerinckia sp. microencapsulated in different carbohydrates.

This study examined the possibility of preserving Beijerinckia cultures by encapsulation using a spray drier, for use in biotechnological processes in the production of biopolymers. An adequate choice of the wall (coating) material is one of the factors that will determine the degree of cell survival and the maintenance of fermentative activity in the encapsulated inoculum. Malt dextrin, dehydrated glucose syrups, modified starch, and acacia (gum arabic) were used as wall materials. The results showed that spray-dried Beijerinckia encapsulated in malt dextrin, stored for 2 mo, and inoculated into sterile must after rehydration presented the greatest stability with respect to fermentative activity, although the glucose-encapsulated cells showed the highest percentage of viability during spray drying and during the storage period.

Beijerinckia derxii releases plant growth regulators and amino acids in synthetic media independent of nitrogenase activity.

AIMS: This study aims at evaluating the ability of Beijerinckia derxii, a free-living nitrogen (N)-fixing bacterium frequently isolated from tropical soils, to release certain plant growth regulators [indoleacetic acid (IAA), ethylene, polyamines] and amino acids into the growth medium. METHODS AND RESULTS: The production of those substances was compared using both cultures in which nitrogenase was active (N-free medium) and cultures in which nitrogenase was repressed (combined-N cultures). Those cultures were grown under agitation and in absence of agitation. Total IAA production was higher in agitated, N-free cultures but specific production was greater in combined-N cultures under agitation. Putrescine and spermidine were detected under all conditions tested. Ethylene was produced in both N-free and combined-N cultures. A greatest diversity of amino acids was released in N-free cultures. CONCLUSIONS: There was no inhibition of the production of the analysed substances under conditions where nitrogenase was inactive. SIGNIFICANCE AND IMPACT OF THE STUDY: Beijerinckia derxii is potentially a producer of plant-active substances; its presence in the natural environment suggests that this bacterium may contribute to the development of other living organisms.

During stationary phase, Beijerinckia derxii shows nitrogenase activity concomitant with the release and accumulation of nitrogenated substances.

Beijerinckia derxii, a free-living nitrogen-fixing bacterium, maintained an increasing nitrogenase specific activity during the stationary growth phase. To verify the destination of the nitrogen fixed during this phase, intra and extracellular nitrogenated contents were analyzed. Organic nitrogen and amino acids were detected in the supernatant of the cultures. An increase in intracellular content of both nitrogen and protein occurred. Cytoplasmic granules indicated the presence of arginine. The ability of a non-diazotrophic bacterium (E. coli) to use B. derxii proteins as a source of nitrogen was observed concomitantly with E. coli growth. There is a suggestion that B. derxii contributes to the environment by both releasing nitrogenated substances and accumulating substances capable of being consumed after its death.