Proposal of Henriciella barbarensis sp. nov. and Henriciella algicola sp. nov., stalked species of the genus and emendation of the genus Henriciella.

Two Gram-negative, heterotrophic, aerobic, prosthecated, marine bacteria, designated strains MCS23T and MCS27T, were isolated from seawater samples. NaCl was required for growth. The major polar lipid detected in strain MCS27T was phosphatidylglycerol, whereas those detected in MCS23T were phosphatidylglycerol, sulfoquinovosyl diacylglycerol and 1,2-diacyl-3-α-d-glucuronopyranosyl-sn-glycerol taurineamide. The most abundant cellular fatty acids were C18 : 1ω7 and C16 : 0, hydroxyl-fatty acids were 3-OH C12 : 0 in both strains and 3-OH C11 : 0 in MCS23T. Strains MCS23T and MCS27T had DNA G+C contents of 57.0 and 55.0 mol%, respectively. The two strains shared 99.3 % 16S rRNA gene sequence similarity; levels of similarity with the type strains of species of the genus Henriciella were 99.4-97.8 % but DNA-DNA hybridizations were 53 % or lower. Besides their 16S rRNA gene sequences, the novel strains can be differentiated from other species of the genus Henriciella by cell morphology, lipid and fatty acid patterns and enzyme activities. The data obtained led to the identification of two novel species, for which the names Henriciella barbarensis sp. nov. (type strain MCS23T=LMG 28705T=CCUG 66934T) and Henriciella algicola sp. nov. (type strain MCS27T=LMG 29152T=CCUG 67844T) are proposed. As these two novel species are the first prosthecate species in the genus Henriciella, an emended genus description is also provided.

Aurantiogliocladin inhibits biofilm formation at subtoxic concentrations.

Infections where pathogens are organized in biofilms are difficult to treat due to increased antibiotic resistances in biofilms. To overcome this limitation new approaches are needed to control biofilms. One way is to screen natural products from organisms living in a wet environment. The rational is that these organisms are preferentially threatened by biofilm formation and may have developed strategies to control pathogens in these biofilms. In a screen of fungal isolates obtained from the Harz mountains in Germany several strains have been found producing compounds for the inhibition of biofilms. One of these strains has been identified as Clonostachys candelabrum producing aurantiogliocladin. Biological tests showed aurantiogliocladin as a weak antibiotic which was active against Staphylococcus epidermidis but not S. aureus. Aurantiogliocladin could also inhibit biofilm formation of several of the tested bacterial strains. This inhibition, however, was never complete but biofilm inhibition activity was also found at concentrations below the minimal inhibitory concentrations, e. g. Bacillus cereus with a MIC of 128 µg mL-1 showed at 32 µg mL-1 still 37% biofilm inhibition. In agreement with this finding was the observation that aurantiogliocladin was bacteriostatic for the tested bacteria but not bactericidal. Because several closely related toluquinones with different antibiotic activities have been reported from various fungi screening of a chemical library of toluquinones is suggested for the improvement of biofilm inhibition activities.