Morphogenesis and adhesion of Aureobasidium pullulans

1994 ◽  
Vol 40 (1) ◽  
pp. 6-17 ◽  
Author(s):  
John H. Andrews ◽  
Robin F. Harris ◽  
Russell N. Spear ◽  
Gee W. Lau ◽  
Erik V. Nordheim

Two strains of the dimorphic fungus Aureobasidium pullulans were grown in liquid and on solid media varying in carbon and nitrogen content, and on leaf surfaces. Hyphae were observed in all systems but comprised a very low proportion (often below quantitative detection) of the total biomass. In liquid media, hyphae were found sparsely and only in the wash-zone on walls of the culture flasks. Yeast phase growth (blastospores) occurred in pH-buffered media that were nutrient balanced, or continuously carbon-limited (fed-batch culture), or carbon-exhausted (batch culture). Blastospores exposed to conditions with limited nitrogen but sufficient organic carbon, or to acidified media, converted to swollen cells and chlamydospores. The latter morphotypes accumulated carbon internally as lipid granules, and then externally as capsular and soluble extracellular polysaccharide. They were cohesive and also adhered more strongly to cellulose membranes overlying agar media or to leaves than did blastospores. Pullulanase treatment diminished the capsules, cohesion, and adhesion. Addition of soluble extracellular polysaccharide to blastospores enhanced their adhesion to leaves. We conclude that extracellular polysaccharide can play a role in adhesion of A. pullulans.Key words: phylloplane, leaf surface, epiphytic growth, extracellular polysaccharide, cell attachment.

2010 ◽  
Vol 192 (23) ◽  
pp. 6287-6290 ◽  
Author(s):  
Lucas B. Pontel ◽  
Alejandro Pezza ◽  
Fernando C. Soncini

ABSTRACT Salmonella ΔcuiD strains form mucoid colonies on copper-containing solid media. We show here that this multiaggregative behavior is caused by the Rcs-dependent induction of colanic acid extracellular polysaccharide. Deletion of cps operon genes in a ΔcuiD strain increased the sensitivity to copper, indicating a role for colanic acid in copper resistance.


2011 ◽  
Vol 63 (4) ◽  
pp. 689-694 ◽  
Author(s):  
G. A. C. Ehlers ◽  
S. J. Turner

The influence and dynamics of bacterial extracellular polysaccharide (EPS) polymer production and its impact on bioflocculation in activated sludge (AS) bench-scale reactors were investigated. The impact of food to microorganism ratio (F/M), reactor configuration and easily biodegradable carbohydrates in influent streams on biological processes that support or weaken good floc formation and the link with EPS quantity was studied. Bioreactors were run as either sequencing batch or continuous systems using wastewater media with glucose or acetate as C source in different F/M ratios. EPS levels were quantified using mid-infrared spectroscopy which provided a rapid technique for monitoring biological processes within AS WWTP. The analysis revealed an interdependent link between EPS production, sludge settling characteristics and mode of reactor operation. An inverse relationship between F/M ratios and EPS quantities was seen but a positive link between EPS levels and aggregation indices, a measure of the efficiency of inter cell attachment and which indicates good settling properties, was also seen. This indicates that during high F/M conditions in lab-scale AS reactors, low levels of EPS may be produced which could have a negative impact on settling of the biomass. Floc architecture was examined under the microscope. Transient growth of filamentous bacteria was seen in the reactors.


2005 ◽  
Vol 4 (12) ◽  
pp. 1982-1989 ◽  
Author(s):  
Jarrod R. Fortwendel ◽  
Wei Zhao ◽  
Ruchi Bhabhra ◽  
Steven Park ◽  
David S. Perlin ◽  
...  

ABSTRACT The Ras family of GTPase proteins has been shown to control morphogenesis in many organisms, including several species of pathogenic fungi. In a previous study, we identified a gene encoding a fungus-specific Ras subfamily homolog, rasB, in Aspergillus fumigatus. Here we report that deletion of A. fumigatus rasB caused decreased germination and growth rates on solid media but had no effect on total biomass accumulation after 24 h of growth in liquid culture. The ΔrasB mutant had an irregular hyphal morphology characterized by increased branching. Expression of rasBΔ113-135, a mutant transgene lacking the conserved rasB internal amino acid insertion, did not complement the deletion phenotype of delayed growth and germination rates and abnormal hyphal morphology. Virulence of the rasB deletion strain was diminished; mice infected with this strain exhibited ∼65% survival compared to ∼10% with wild-type and reconstituted strains. These data support the hypothesis that rasB homologs, which are highly conserved among fungi that undergo hyphal growth, control signaling modules important to the directional growth of fungal hyphae.


Author(s):  
Tina Schwach ◽  
E. A. Zottola

LVSEM offers the microbiologist a unique view of the microbial cell surface. Colony morphology is used by microbiologists to distinguish between organisms. Some bacteria exhibit different colony morphologies when grown on solid media. P. fragi ATCC 4973 exhibits both rough (R) and smooth (S) colonies. It is not known why different morphologies form, but there is some speculation that their expression may be affected by nutrient conditions,other physical parameters, such as growth in a nonstatic environment, and may involve extracellular polysaccharide (EPS) formation. EPS has also been implicated in bacterial attachment to surfaces.In this study, three organisms of importance to the food industry were grown in Trypticase Soy Broth (TSB) at 21C. Growth rates, EPS production, and cell surface morphologies were evaluated in both 3% TSB and 0.3% TSB. The lower concentration was used to simulate decreased availability of nutrients. Two glass chips (3mm × 6mm) were added to small petri dishes containing the culture medium and the organism.


2015 ◽  
Vol 127 ◽  
pp. 325-331 ◽  
Author(s):  
Dahui Wang ◽  
Feifei Chen ◽  
Gongyuan Wei ◽  
Min Jiang ◽  
Mingsheng Dong

2019 ◽  
Author(s):  
Haichao Guo ◽  
Larry M. York

ABSTRACTPrevious simulations indicated reduced nodal root number (NRN) was promising for maize (Zea mays L.) breeding, and were partially confirmed using variation in NRN among inbreds. However, the exact mechanism was unknown, therefore manipulative experiments were conducted in hydroponics and tall solid-media mesocosms with treatments involving no nodal root excision (0% NRE) or excising either 33% or 67% of the nodal roots (NR) as they emerged under high or low levels of nitrogen (N). Reduced NRN was hypothesized to increase elongation of all remaining root classes, increase N acquisition under low N, and increase shoot mass. In both experiments, plants with 67% NRE had 12% and 19% less root fraction of total biomass, 61% and 91% greater lateral-to-axial root length ratio regardless of N levels; and 61% and 182% greater biomass of embryonic roots under low N, compared to 0% NRE for hydroponics and mesocosms studies, respectively. In hydroponics, regardless of NRE level, specific root respiration under high N was 2.6 times of low N, and was greatest at depth. Under low N in mesocosms, plants with 67% NRE had 52% greater shoot biomass, 450% greater root length at depth, and 232% greater deep-injected 15N content in the shoot relative to 0% NRE, however biomass in hydroponics did not differ based on NRE. These results reveal the mechanism by which plants with fewer nodal roots increase N capture and shoot mass by reallocation of biomass to lateral, embryonic, and first whorl nodal roots that increases foraging efficiency in solid media.SummaryReallocating root biomass from nodal roots to lateral and early-emerging axial roots allows grasses to capture more nitrogen under limiting conditions, including by increasing foraging at depth.


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