b Leaf-cutter ants use plant matter to culture the obligate mutualistic basidiomycete Leucoagaricus gongylophorus. This fungus mediates ant nutrition on plant resources. Furthermore, other microbes living in the fungus garden might also contribute to plant digestion. The fungus garden comprises a young sector with recently incorporated leaf fragments and an old sector with partially digested plant matter. Here, we show that the young and old sectors of the grass-cutter Atta bisphaerica fungus garden operate as a biphasic solid-state mixed fermenting system. An initial plant digestion phase occurred in the young sector in the fungus garden periphery, with prevailing hemicellulose and starch degradation into arabinose, mannose, xylose, and glucose. These products support fast microbial growth but were mostly converted into four polyols. Three polyols, mannitol, arabitol, and inositol, were secreted by L. gongylophorus, and a fourth polyol, sorbitol, was likely secreted by another, unidentified, microbe. A second plant digestion phase occurred in the old sector, located in the fungus garden core, comprising stocks of microbial biomass growing slowly on monosaccharides and polyols. This biphasic operation was efficient in mediating symbiotic nutrition on plant matter: the microbes, accounting for 4% of the fungus garden biomass, converted plant matter biomass into monosaccharides and polyols, which were completely consumed by the resident ants and microbes. However, when consumption was inhibited through laboratory manipulation, most of the plant polysaccharides were degraded, products rapidly accumulated, and yields could be preferentially switched between polyols and monosaccharides. This feature might be useful in biotechnology. In the nests of leaf-cutter ants of the genera Atta and Acromyrmex, gardens of the obligate mutualistic basidiomycete fungus Leucoagaricus gongylophorus (1, 2) are cultivated on fresh vegetal materials (3-5). Although few leaf-cutter species prefer monocots, most leaf-cutter ants collect plant materials from both monocots and dicots (6). The ants collect and transport these plants to their nests and then fractionate and extensively clean the leaf fragments (7,8). Subsequently, the ants deposit a drop of fecal fluid onto the leaf fragment surface and inoculate the leaf fragment with L. gongylophorus hyphae. The plant-digesting enzymes in the fecal fluid facilitate fungal development (9). This fungus produces swollen hyphal tips, called gongylidia, that cluster together to form macroscopic structures known as staphylae, which are food sources for the ants (3-5). L. gongylophorus also secretes enzymes that act synergistically with ant enzymes to degrade plant matter, generating soluble compounds that are subsequently ingested by the ants (10-13). These enzymes attack plant polysaccharides, including starch, hemicellulose, pectin, and, to a lesser extent, cellulose (10,(14)(15)(16)(17)(18)(19)(20)(21)(22)(23). In addition, other microbes living in the fungus garden might mediate ant nutrition...
Aspergillus versicolor grown on xylan or xylose produces two beta-xylosidases with differences in biochemical properties and degree of glycosylation. We investigated the alterations in the biochemical properties of these beta-xylosidases after deglycosylation with Endo-H or PNGase F. After deglycosylation, both enzymes migrated faster in PAGE or SDS-PAGE exhibiting the same R(f). Temperature optimum of xylan-induced and xylose-induced beta-xylosidases was 45 degrees C and 40 degrees C, respectively, and 35 degrees C after deglycosylation. The xylan-induced enzyme was more active at acidic pH. After deglycosylation, both enzymes had the same pH optimum of 6.0. Thermal resistance at 55 degrees C showed half-life of 15 min and 9 min for xylose- and xylan-induced enzymes, respectively. After deglycosylation, both enzymes exhibited half-lives of 7.5 min. Native enzymes exhibited different responses to ions, while deglycosylated enzymes exhibited identical responses. Limited proteolysis yielded similar polypeptide profiles for the deglycosylated enzymes, suggesting a common polypeptide core with differential glycosylation apparently responsible for their biochemical and biophysical differences.
In animals, the storage of body reserves results from a positive balance of energy, which is used for daily activities (Willmer et al. 1988). In insects, the body reserves are mostly in the body fat (lipid reserves) or in the hemolymph, such as free carbohydrates. The sugars in the hemolymph are mainly in the form of trehalose, a disaccharide composed of two glucose molecules (Thompson 2003).Social insects transport the food collected in the external environment to the nest, in order to share it with the other nestmates. For this reason, carbohydrate concentrations in the body vary not only with the dietary habits, but also with the social organization of the species. For example, in honeybees, a well-studied organism, the body concentration of carbohydrates depends on the composition of the sugars consumed, the metabolic rate of individuals, and the season (nectar availability of natural origin) (Blatt & Roces 2001). In ants, little is known about the levels of sugars in the hemolymph, as well as its relationship with the energy for behavioral activities.In Camponotus rufipes (Fabricius, 1775), a species that feeds on nectar, the levels of sugars in the hemolymph and the behavioral status of individuals are correlated (Schilman & Roces 2008): immobile ants have higher levels of trehalose and fructose than active ants. This suggests that the concentration of sugars can act as a feedback mechanism, encouraging individuals with different nutritional statuses to forage, and thus promote a rotation in the execution of tasks (Thompson 2003).In leaf cutting ants, the diet is composed of soluble carbohydrates from hyphae of the fungus garden, cultivated by the colony (Silva et al 2003). Although the fungus garden constitute a high energy food source, some activities performed by ants are probably very energy consuming. Among them stands out the excavation of the nest, initiated by the queen (nest foundation), and later on carried out by the workers. So far, we know more about nest structure than about the effort of digging the nest, and how much energy is expended by those involved in building and maintaining nest structures.In this study we endeavored to answer the following question: Which storage body reserves are used to fuel digging activity, and to what degree? In order to find out the answer we determined the content of body reserves of workers (total carbohydrates and lipids) before and after nest excavation. MATERIAL AND METHODSNest excavation by workers. Five laboratory colonies of Atta sexdens (Linnaeus, 1758) were used as source of workers, with head width varying between 1.2 to 1.6 mm. Workers within this size range are known to be responsible for the excavation of the nest (Camargo et al 2012). The ambient temperature was maintained at approximately 24 ± 2°C, with a relative humidity of 70 ± 20%. The colonies were fed with Ligustrum spp. and Acalypha spp. throughout the experiment. ABSTRACT. Energy substrate used by workers of leaf-cutting ants during nest excavation. In this study we aimed to ascertain w...
Statistical evidence pointing to the very soft change in the ionic composition on the surface of the sugar cane bagasse is crucial to improve yields of sugars by hydrolytic saccharification. Removal of Li+ by pretreatments exposing -OH sites was the most important factor related to the increase of saccharification yields using enzyme cocktails. Steam Explosion and Microwave:H2SO4 pretreatments produced unrelated structural changes, but similar ionic distribution patterns. Both increased the saccharification yield 1.74-fold. NaOH produced structural changes related to Steam Explosion, but released surface-bounded Li+ obtaining 2.04-fold more reducing sugars than the control. In turn, the higher amounts in relative concentration and periodic structures of Li+ on the surface observed in the control or after the pretreatment with Ethanol:DMSO:Ammonium Oxalate, blocked -OH and O− available for ionic sputtering. These changes correlated to 1.90-fold decrease in saccharification yields. Li+ was an activator in solution, but its presence and distribution pattern on the substrate was prejudicial to the saccharification. Apparently, it acts as a phase-dependent modulator of enzyme activity. Therefore, no correlations were found between structural changes and the efficiency of the enzymatic cocktail used. However, there were correlations between the Li+ distribution patterns and the enzymatic activities that should to be shown.
The effect of several nutritional and environmental parameters on Penicillium purpurogenum growth and sacharogenic amylase production was analyzed. High enzyme levels (68.2 U mg-1) were obtained with Khanna medium at initial pH 6.0, incubated at 30ºC for 144 hours. The optimum pH and temperature activities were 5.0 and 65ºC, respectively. The enzyme presented a half-life (t50) of 60 min, at 65ºC. Only glucose was detected after 24 hours of reaction using soluble starch as substrate
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