Two methods for isolation of endophytic and edaphic Bacillus spp. from sugarcane fields / Dois métodos para isolamento de Bacillus spp. endofíticos e edáficos de canaviais

Bacillus has been widely studied and used for the control of pests and diseases. The adapted protocol proposed by POLANCZYK (2004) proved to be more efficient than the one by the World Health Organization (WHO, 1985) to isolate edaphic strains of Bacillus. However, it has not been assessed for isolation of endophytic strains, which are much less abundant in the nature and more difficult to be isolated. This study aimed to compare two methodological procedures for isolation of Bacillus, established by the WHO (1985) and by POLANCZYK (2004), regarding their efficiency for isolation of endophytics and edaphics Bacillus strains from inside the root tissue of sugarcane, as well as from the associated soil sample, collected from 11 locations; and to compare the density of bacteria in both environments. Endophytic and edaphic strains of Bacillus were isolated by both procedures. However, the isolation protocol performed by POLANCZYK (2004) made more efficient by having a greater number of colony forming units (CFU) per gram of soil and root indicating that this procedure is more useful, especially for isolation of endophytic strains of Bacillus, which are much less abundant in the nature than edaphic strains, being therefore more difficult to be isolated. Using the Polanczyk protocol (2004), Bacillus strains were recovered from all roots (endophytic) and soil (edaphic) samples of all the 11 fields, suggesting that the plant root may be another important source for isolation of Bacillus besides the soil. Higher densities of Bacillus were isolated from the edaphic environment compared with the endophytic environment, with significant differences when isolated by Polanczyk method (2004).(AU)

Bacillus tem sido amplamente estudado e usado para o controle de pragas e doenças. O protocolo adaptado proposto por POLANCZYK (2004) mostrou-se mais eficiente do que o da Organização Mundial de Saúde (WHO, 1985) para isolar cepas edáficas de Bacillus. No entanto, não foi avaliado quanto ao isolamento de estirpes endofíticas, que são muito menos abundantes na natureza e mais difíceis de isolar. Este estudo teve como objetivos comparar dois procedimentos metodológicos para o isolamento de Bacillus, o estabelecido pela OMS (WHO, 1985) e o de POLANCZYK (2004), quanto a sua eficiência para o isolamento de estirpes endofitas e edáficas de Bacillus originárias do interior do tecido radicular de cana-de-açúcar, bem como de amostras de solos associados, coletada de 11 locais; e comparar a densidade de bactérias em ambos os ambientes. As cepas endofíticas e edáficas de Bacillus foram isoladas por ambos os procedimentos. No entanto, o protocolo de isolamento realizado por POLANCZYK (2004) demonstrou-se mais eficiente por gerar maior número de unidades de formação de colônias (CFU) por grama de solo e raiz, indicando que esse procedimento é mais útil, especialmente para isolamento de estirpes endofíticas de Bacillus, que são muito menos abundantes na natureza do que as cepas edáficas, sendo, portanto, mais difíceis de serem isoladas. Usando o protocolo de POLANCZYK (2004), as cepas de Bacillus foram isoladas de todas as amostras de raízes (endofíticas) e de solo (edáficas) de todos os 11 campos, sugerindo que a raiz da planta pode ser outra fonte importante de isolamento de Bacillus além do solo. As densidades mais altas de Bacillus foram isoladas do ambiente edáfico em comparação com o ambiente endofítico, com diferenças significativas quando isoladas pelo método de POLANCZYK (2004).(AU)

Effects of inoculation with soil bacteria on growth of Rehmannia glutinosa in tube and potted plantlets / 中草药

Objective To investigate the cause of continuous cropping obstacle of Rehmannia glutinosa and screen beneficial bacteria.Methods In vitro cultured plantlets and potted plants were inoculated with different isolated soil bacteria. The plants were harvested and weighted in 30 and 60 d,respectively.Results In the in vitro culture experiment,11 out of 48 strains displayed promoting action on the growth of plantlets,and 11 other strains showed inhibitory or lethal action.In the potted test,16 strains showed promoting action and 13 strains showed suppressing or lethal action.Conclusion Soil bacteria influence the growth of R.glutinosa significantly.The flora of rhizosphere bacteria may be disturbed by the cultivation of R.glutinosa and inoculation of beneficial bacteria might be effective on the resolution of continuous cropping obstacle of R.glutinosa.

The Dynamic Changes of Soil Beneficial Bacteria in Cotton Continuous Cropping Soil South Xinjiang / 微生物学通报

To research the effect of continuous cropping on cotton soil microorganisms and soil microorgan-isms on grow of cotton,we studied the total numbers of aerobic self-nitrogen-fixing bacteria,potassium bacteria,cellulose decomposing bacteria,phosphate solubilizing bacteria,organic-phosphorus-dissolving bacteria distributed in continuous cropping cotton fields of regimental farm 2 and 3 of the first agricultural division through dilution spread plate method.Results showed that the total numbers of five kinds of bacte-ria was highest in blooming and bolling periods,lowest in seeding periods and higher in before sowing pe-riods.The total numbers of five kinds of bacteria was no notable regular changes with continuous cropping year.The numbers of aerobic self-nitrogen-fixing bacteria at different cotton growth stages in regimental farm 2 was higher than in regimental farm 3 and the numbers change of other bacteria was varied in different cotton growth stages in regimental farm 2 and 3.Soil beneficial bacteria were negatively correlated with a variety of soil nutrient ion and free-living nitrogen fixing bacteria were significantly positive correlated with soil total nitrogen.