Morphological Instabilities in a growing Yeast Colony: Experiment and Theory

We study the growth of colonies of the yeast Pichia membranaefaciens on agarose film. The growth conditions are controlled in a setup where nutrients are supplied through an agarose film suspended over a solution of nutrients. As the thickness of the agarose film is varied, the morphology of the front of the colony changes. The growth of the front is modeled by coupling it to a diffusive field of inhibitory metabolites. Qualitative agreement with experiments suggests that such a coupling is responsible for the observed instability of the front.Comment: RevTex, 4 pages and 3 figure

Millisia

Mil.li'si.a N.L. fem. n. named after Nancy F. Millis, a celebrated microbiologist who promoted wastewater microbiology in AustraliaActinobacteria / Actinobacteria / Corynebacteriales / Nocardiaceae / MillisiaAerobic, Gram‐stain‐positive to Gram‐stain‐variable, acid–alcohol‐fast, nonmotile, catalase‐positive actinomycete that forms non‐sporing rods which show only rudimentary right‐angled branching and which contain polyphosphate storage granules. In stationary phase, the rods fragment into spherical unicells (Figure 1). Salmon pink, irregular colonies with filamentous margins and sparse unbranched aerial hyphae are formed on glucose‐yeast extract agar. Colonies are matt and dry in appearance, soft in texture, and easy to emulsify. Diffusible pigments are not produced. Whole‐organism hydrolysates are rich in meso‐diaminopimelic acid, arabinose, and galactose. The organism contains N‐glycolated muramic acid residues, a predominant dihydrogenated menaquinone with eight isoprene units, and diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylinositol, and phosphatidylinositol mannosides as major polar lipids. Mycolic acids have 44–52 carbon atoms (principal components C48, C50, and C52), and oleic, palmitic, and palmitoleic acids are the predominant fatty acids, with relatively small amounts of myristic, stearic, and tuberculostearic acids. A member of the family Nocardiaceae in the order Corynebacteriales.DNA G+C content (mol%): 64.7 (HPLC).Type species: Millisia brevis Soddell, Stainsby, Eales, Kroppenstedt, Seviour and Goodfellow 2006a, 742VP.<br/

Dispelling the "Nocardia amarae" myth: a phylogenetic and phenotypic study of mycolic acid-containing actinomycetes isolated from activated sludge foam.

Right-angle branched filaments and rods micromanipulated from activated sludge foam and mixed liquor were identified as putatively novel members of the genera Gordonia, Mycobacterium and Rhodococcus using a combination of chemical, molecular and morphological data. Pyrolysis mass spectrometric analyses of gordoniae isolated in both the present and a previous study revealed pyro-groups, distinct from validly described Gordonia species, which could be equated with those based on morphological properties and 16S rDNA data. Putative gordoniae assigned to one of these groups were found to be closely related to strains currently identified as "Rhodococcus australis". These strains were also found to have properties consistent with their classification in the genus Gordonia. The results of this study highlight the limitations of the microscopic approach to filament identification and cast further doubt on the view that foaming can be attributed to members of one or a few Nocardia species

The opportunistic pathogen Nocardia farcinica is a foam-producing bacterium in activated sludge plants

A Gram-positive unicellular coccal-diphtheroid rod causing foam in an activated sludge plant was successfully isolated by micromanipulation. Phenotypic characterization and 16S rDNA sequencing identified it as Nocardia farcinica. This is the first report that-this opportunistic pathogen is a foam-causing bacterium in activated sludge, and the clinical implications of these observations are discussed

The filamentous bacterial morphotype "Nostocoida limicola" I contains at least two previously described genera in the low G+C Gram positive bacteria.

Isolates of eight bacterial filaments fitting the published morphological description of "Nostocoida limicola" I were obtained from the mixed liquor of four different Australian and one Czech Republic activated sludge plants by micromanipulation. On the basis of their near complete (Ben 200 and Ben 201), or partial (Ben 77, Ben 78, Ben 202, Ben 203, Ben 204 and Ben 205) 16S rRNA gene sequences, six of these isolates were 99.3-100% similar to Lactosphaera pasteurii and Trichococcus flocculiformis, a bulking filament only reported previously in Germany. The other two (Ben 203 and Ben 204) were 99.9% similar to Streptococcus suis. Hence, all are in the low mol % G+C Gram-positive bacteria division of the Bacteria. On this evidence "N. limicola" I is phylogenetically unrelated to "Nostocoida limicola" II, which is now known to be in the Actinobacteria, even though these two filamentous bacteria appearing in activated sludge systems have been considered to be closely related to each other historically

Gordonia defluvii sp. nov., an actinomycete isolated from activated sludge foam.

Three strains of non-motile, Gram-positive, filamentous actinomycetes, isolates J4T, J5 and J59, initially recognized microscopically in activated sludge foam by their distinctive branching patterns, were isolated by micromanipulation. The taxonomic positions of the isolates were determined using a polyphasic approach. Almost-complete 16S rRNA gene sequences of the isolates were aligned with corresponding sequences of representatives of the suborder Corynebacterineae and phylogenetic trees were inferred using three tree-making algorithms. The organisms formed a distinct phyletic line in the Gordonia 16S rRNA gene tree. The three isolates showed 16S rRNA gene sequence similarities within the range 96.9–97.2 % with their nearest phylogenetic neighbours, namely Gordonia bronchialis DSM 43247T and Gordonia terrae DSM 43249T. Strain J4T was shown to have a chemotaxonomic profile typical of the genus Gordonia and was readily distinguished from representatives of the genus on the basis of Curie-point pyrolysis mass spectrometric data. The isolates shared nearly identical phenotypic profiles that distinguished them from representatives of the most closely related Gordonia species. It is evident from the genotypic and phenotypic data that the three isolates belong to a novel Gordonia species. The name proposed for this taxon is Gordonia defluvii sp. nov.; the type strain is J4T (=DSM 44981T=NCIMB 14149T)

Friedmanniella spumicola sp. nov. and Friedmanniella capsulata sp. nov. from activated sludge foam: Gram-positive cocci that grow in aggregates of repeating groups of cocci

Two Gram-positive, non-motile, non-spore-forming, strictly aerobic, pigmented cocci, strains Ben 107T and Ben 108T, growing in aggregates were isolated from activated sludge samples by micromanipulation. Both possessed the rare type A3 gamma' peptidoglycan. Major menaquinones of strain Ben 107T were MK-9(H4) and MK-7(H2), and the main cellular fatty acid was 12-methyltetradecanoic acid (ai-C15:0). In strain Ben 108T, MK-9(H4), MK-9(H2) and MK-7(H4) were the menaquinones and again the main fatty acid was 12-methyltetradecanoic acid (ai-C15:0). Polar lipids in both strains consisted of phosphatidyl inositol, phosphatidyl glycerol and diphosphatidyl glycerol with two other unidentified glycolipids and phospholipids also present in both. These data, together with the 16S rDNA sequence data, suggest that strain Ben 107T belongs to the genus Friedmanniella which presently includes a single recently described species, Friedmanniella antarctica. Although the taxonomic status of strain Ben 108T is far less certain, on the basis of its 16S rRNA sequence it is also adjudged to be best placed in the genus Friedmanniella. The chemotaxonomic characteristics and DNA-DNA hybridization data support the view that Ben 107T and Ben 108T are novel species of the genus Friedmanniella. Hence, it is proposed that strain Ben 107T (= ACM 5121T) is named as Friedmanniella spumicola sp. nov. and strain Ben 108T (= ACM 5120T) as Friedmanniella capsulata sp. nov