Screening Test for Antibiotics in Medicinal Plants(STAMP):Using Powdered Plant Materials Instead of Extracts

Plants are a rich source of antibiotics, but screening all the existing plant species for biological activity using current methods can be time and resource consuming. The present study is to investigate whether powdered plant materials would perform as well as plant extracts in the screening of plants with antimicrobial activity. In the new method proposed (STAMP), we compared in vitro antimicrobial activity of powdered plant materials from 12 species against bacteria and fungi. We confirmed these results with their corresponding aqueous (wet) and hydro-alcoholic extracts and one species testing the antimicrobial activity of two isolated compounds. Compared with hydro-alcoholic extracts, screening using the powdered plant materials correctly identified the majority of the species with antimicrobial activity against Candida albicans (sensitivity 91%, specificity 86%), C. parapsilosis (sensitivity 100%, specificity 67%), and Staphylococcus aureus (sensitivity 64%, specificity 86%). For bacteria, the method performed better in a pH of 9.0. The antimicrobial activity of two compounds isolated from one species (maytenin and netzahualcoyone) confirmed the results. In conclusion, the use of powdered plant materials for screening plants with antimicrobial properties is a cheap, widely available, technically easy, time sparing, reproducible, and sensitive method and can significantly shorten the time and money spent during drug development.

Tree encroachment into savannas alters soil microbiological and chemical properties facilitating forest expansion

Abstract Forests have been expanding over typical savanna sites for the past 3000 years in the Neotropics. Such invasion can produce a series of environmental modifications on typical savanna; however, it remains unclear how modifications in soil properties, caused by the encroachment of woody species, facilitate the expansion of forest ecosystems under dystrophic conditions. Here we examined chemical and microbiological changes associ- ated with tree encroachment in oxisols of a Neotropical Savanna at Assis Ecological Station, Southeastern Brazil. We predicted that tree encroachment caused by typical forest species would cause significant changes in the chemical and microbiological properties of savanna soils. Soils were sampled at Assis Ecological Station, from savanna sites differing in tree encroachment （typical, dense and forested savanna） caused by decades of fire exclusion. We analysed vegetation leaf area index and leaf litter volume deposited in the studied plots and chemical （pH,organic matter, P, K, Ca, Mg, A1, NO3-, NH4＋） and microbiological （microbial C biomass and dehydrogenase activity） properties of soils under distinct encroachment conditions. Most soil chemical properties did not change along the tree encroachment gradient; however, total P, soil organic matter, soil microbial C and dehydrogenase activity increased from typical savanna to forested savanna. The changes in soil organic matter and dehydrogenase activity were correlated with the values of leaf area index and litter volume along the encroachment gradient. Our results demonstrate that forest species can increase carbon and phosphorus supplies in tropical savanna soils.

The nest architecture of the ant, Pheidole oxyops Forel, 1908 （Hymenoptera： Formicidae）

Pheidole oxyops builds subterranean nests, with an external architecture that is distinctive and easily recognizable by its wide and specific entrance hole, measuring up to 12.2 cm in diameter, denoting a pitfall-trap. In order to study the nests＇ internal architecture, seven nests were excavated; four were identified with neutral talc, while the others were cast in cement and then excavated. Measurements were made in order to gain a better understand- ing of their structures, and a photographic documentation was obtained as well. The excavations revealed that the nests are perpendicular relative to the ground, beginning with a cylindrical channel with a mean length of 13.5 cm, containing irregular formations, and whose diameter becomes progressively narrower until the first chamber is formed. As the channel continues, dish-like chambers appear, interconnected by channels that become progressively narrower and longer, while the chambers are arranged at greater distances from each other as nest depth increases. Both channels and chambers are located on the vertical projection of the entrance hole. Nests may reach a depth of up to 5.09 m, with a number of chambers ranging between 4 and 14.