Paenibacillus agarexedens sp. nov., nom. rev., and Paenibacillus agaridevorans sp. nov.

Twenty-two agarolytic, aerobic, spore-forming strains were characterized taxonomically by DNA-DNA reassociation experiments, riboprint analyses, 16S rDNA sequencing and phenetic similarity analyses. Based on riboprint analyses, the strains formed eight ribogroups, six of which contained 2-6 strains and two encompassed single strains. Within the multi-strain ribogroups, similarities ranged from 91-99%. Phylogenetic analyses of representatives of the eight groups by 16S rDNA sequence analysis showed that the strains were affiliated to the genus Paenibacillus, but relatedness to described Paenibacillus species was only moderate (<97.8% sequence similarity). Published DNA-DNA similarity values for most of the agarolytic strains, supplemented with new data, supported the distinctiveness of the eight ribogroups. Intragroup DNA-DNA similarity values ranged from 80 to 104%, while intergroup DNA-DNA similarities were <35%. Based on genomic distinctiveness and supported by the presence of distinguishing phenotypic properties, multi-strain groups 1 and 2 are proposed as novel species, Paenibacillus agarexedens sp. nov., nom. rev. (type strain, DSM 1327T=CIP 107437T) and Paenibacillus agaridevorans sp. nov. (type strain, DSM 1355T=CIP 107436T).

Application of flow cytometry to rapid microbial analysis in food and drinks industries.

In food and drinks industries, the time required for conventional tests can lead to substantial delays in product release to the market. Flow cytometry (FCM) has been used in conjunction with viability markers for rapid counting of yeast, mould and bacterial cells in food products. A single-parameter flow cytometer has proved applicable to the rapid detection of low numbers of microbial contaminants in finished products. The excellent correlation between FCM results and product quality shelf-life expiry date has allowed the establishment of realistic quality control criteria for rapid positive release of product. Used for the monitoring of microbial biomass during manufacturing processes, flow cytometry allowed a direct assessment of bacterial growth. The reproducibility of the results and the proven correlation with standard plate count method obtained in industrial conditions make FCM a good predictive method for product and process quality control.

[Quantitative recovery of bacteria from different germ carrier materials]. / Quantitative Keimrückgewinnung bei unterschiedlichen Keimträgermaterialien.

A number of germ carriers have been tested quantitatively, in order to select the optimum germ carrier for future quantitative tests of chemical disinfectants, belonging to the class of surface and instrument disinfectants. Quality criteria applied were the storage capacity of the carrier and the germ recovery fraction. For the surface disinfectant, the cotton piece was confirmed to be suited best, while for the instrument disinfection the mineralized soft rubber tube proved to be optimal. The cotton piece, however, stores ten times more germs than the rubber tube which means that with the former, reduction factors of as high as log 6 (-7) can be measured.

[The effectiveness of disinfectants from kinetic viewpoints]. / Die Wirksamkeit von Desinfektionsmitteln unter kinetischen Gesichtspunkten.

In a pilot project, two instrumental disinfectants were tested quantitatively in germ carrier experiments. The disinfectants chosen belonged to the class of aldehydes. The germ carriers comprised wet and dried cotton pieces as well as mineralized soft rubber tubes. The germs tested were Staphylococcus aureus and Pseudomonas aeruginosa. The germs were exposed to 3 (4) different concentrations of the disinfectants. In each case, 4 exposure times were applied, the germs were counted before and after exposure with a Spiralmeter. In order to rationalize the presentation of the 336 experimental data, a kinetic approach was applied. According to the latter, the efficiency of a (aldehyde) disinfectant can be described by a single quantity alpha = RF/C0t, where RF is the reduction factor and C0t the product of the initial concentration of the disinfectant C0 and the exposure time t. Alpha is shown to be independent of C0 and t, as long as the initial concentration has been chosen high enough so that the consumption of the disinfectant during exposure can be neglected. At low concentrations and with wet cotton pieces, the (local) consumption of the disinfectant leads to a drastic deceleration of the killing rates, an effect that has been ascribed to anomalous resistance of the germ populations. However, this effect is not observed in the case of dry germ carriers which disproves this hypothesis. It would be interesting to check whether the above described kinetic approach also can be applied to experiments like the suspension experiments, and whether it is valid also for other chemical groups of disinfectants like the phenols.

Reisolation and growth conditions of bacillus agar-exedens.

Several agarolytic Bacillus strains have been isolated. The properties agree with those described by Wieringa (1941) for Bacillus agar-exedens. These strains are the first reisolates since the original cultures were lost. A second group of isolates is related to the agarolytic B. palustris var. gelaticus of Sickles and Shaw (1934). B. agar-exedens requires carbohydrates for growth. In mineral-glucose media growth is inhibited by peptone at pH values of about 7 or less. Under alkaline conditions no inhibition by peptone is observed. A method for the enrichment of B. agar-exedens is described.