Bioactivity and botanical origin of Austroplebeia and Tetragonula Australian pot-pollen

Antibacterial properties, antioxidant activity, and bioactive components were measured in ethanolic and methanolic extracts of pot-pollen from Australian stingless bees (Meliponini) Austroplebeia australis, Tetragonula carbonaria, and Tetragonula hockingsi. Tetragonula hockingsi pot-pollen presented the highest flavonoid, polyphenol, and protein concentrations in both ethanolic and methanolic extracts. The antioxidant activity was positively correlated with the polyphenol content. All three pot-pollen extracts were active against both Gram-positive (Staphylococcus aureus, Bacillus subtilis) and Gram-negative bacteria (Enterobacter cloacae, Escherichia coli, Pseudomonas aeruginosa), with lower minimum inhibitory concentration (MIC) values found in ethanolic extracts than in methanolic extracts. Ethanolic extracts of Tetragonula hockingsi pot-pollen showed the lowest MIC values. A palynological study identified the botanical origin of Australian pot-pollen. We suggest pot-pollen is a food that increases the value of stingless bee products in Australia

Isolation and characterization of mineral phosphate-solubilizing bacteria naturally colonizing a limonitic crust in the south-eastern Venezuelan region

With the aim to explore the possible role of mineral phosphate-solubilizing bacteria (PSB) in phosphorus (P) cycling in iron-rich, acidic soils, we conducted a survey of PSB naturally colonizing a limonitic crust in the south-east region of Venezuela (Bolívar State). A total of 130 heterotrophic bacterial isolates showing different degrees of mineral tri-calcium phosphate (Ca3(PO4)2)-solubilizing activities were isolated from NBRIP plates. In contrast, no isolates showing iron phosphate (FePO4)- or aluminum phosphate (AlPO4)-solubilizing activities were detected by this experimental approach. The 10 best Ca3(PO4)2-solubilizers were selected for further characterization. These isolates were shown to belong to the genera Burkholderia, Serratia, Ralstonia and Pantoea by partial sequencing analysis of their respective 16S rRNA genes. All the PSB isolates were able to mediate almost complete solubilization of Ca3(PO4)2 in liquid cultures; in contrast, the PSB isolates were less effective when solubilizing FePO4. Two groups of PSB isolates were clearly differentiated on the basis of their Ca3(PO4)2 solubilization kinetics. Acidi.cation of culture supernatants seemed to be the main mechanism for P solubilization. Indeed, gluconic acid was shown to be present in the supernatant of .ve isolates. Furthermore, detection of genes involved in the production of this organic acid was possible in three isolates by means of a PCR protocol.2905–[email protected], [email protected]@[email protected]

Characterization of the mineral phosphate-solubilizing activity of pantoea aglomerans MMB051 isolated from an Iron-Rich soil in southeastern Venezuela (Bolívar State)

The mineral phosphate-solubilizing (MPS) activity of a Pantoea agglomerans strain, namely MMB051, isolated from an iron-rich, acidic soil near Ciudad Piar (Bolý´var State, Venezuela), was characterized on a chemically defined medium (NBRIP). Various insoluble inorganic phosphates, including tri-calcium phosphate [Ca3(PO4)2], iron phosphate (FePO4), aluminum phosphate (AlPO4), and Rock Phosphate (RP) were tested as sole sources of P for bacterial growth. Solubilization of Ca3(PO4)2 was very efficient and depended on acidification of the external milieu when MMB051 cells were grown in the presence of glucose. This was also the case when RP was used as the sole P source. On the other hand, the solubilization efficiency toward more insoluble mineral phosphates (FePO4 and AlPO4) was shown to be very low. Even though gluconic acid (GA) was detected on culture supernatants of strain MMB051, a consequence of the direct oxidation pathway of glucose, inorganic-P solubilization seemed also to be related to other processes dependent on active cell growth. Among these, proton release by ammonium (NH4) fixation appeared to be of paramount importance to explain inorganic-P solubilization mediated by strain MMB051. On the contrary, the presence of nitrate (NO3) salts as the sole N source affected negatively the ability of MMB051 cells to solubilize inorganic [email protected], [email protected]@[email protected]@ula.v