Selection of diazotrophic bacteria isolated from wastewater treatment plant sludge at a poultry slaughterhouse for their effect on maize plants

Abstract

The economic and environmental costs of nitrogen fertilization have intensified the search for technologies that reduce mineral fertilization, for example atmospheric nitrogen-fixing (diazotrophic) bacteria inoculation. In this context, the present study addressed the isolation and quantification of diazotrophic bacteria in the sludge from treated wastewater of a poultry slaughterhouse; a description of the bacteria, based on cell and colony morphology; and an assessment of growth and N content of maize plants in response to inoculation. Sixteen morphotypes of bacteria were isolated in six N-free culture media (JMV, JMVL, NFb, JNFb, LGI, and LGI-P). The bacteria stained gram-positive, with 10 rod- and six coccoid-shaped isolates. To evaluate the potential of bacteria to promote plant growth, maize seeds were inoculated. The experiment consisted of 17 treatments (control plus 16 bacterial isolates) and was carried out in a completely randomized design with six replicates. The experimental units consisted of one pot containing two maize plants in a greenhouse. Forty-five days after planting, the variables plant height, leaf number, stem diameter, root and shoot fresh and dry weight, and N content were measured. The highest values were obtained with isolate UFV L-162, which produced 0.68 g total dry matter per plant and increased N content to 22.14 mg/plant, representing increments of 74 and 133%, respectively, compared with the control. Diazotrophs inhabit sludge from treated wastewater of poultry slaughterhouses and can potentially be used to stimulate plant development and enrich inoculants.

Screening of beneficial bacteria associated with Calophyllum brasiliense Cambess so as to develop microbial inoculants for agriculture

“…Isolates were subcultured on DYGS semi-solid and specific medium, consecutively, for 24 h at 30 ºC, with the purpose of evaluating the morphological characteristics of both colonies and bacterial cells according to Lozada et al (2018). An isolate code was thus assigned to identify the bacteria as follows: the origin of the material used (Root = RO; Aerial part = AP; Rhizosphere = RHI); the culture medium used (JMV, JMVL, NFb, JNFb, LGI and LGI.P); the dilution used (1 = 10 ) and a number to differentiate bacterial strains isolated from the same Petri dish.…”

Selection and agricultural use of potential phosphate-solubilizing bacteria isolated from poultry slaughterhouse sludge in maize

“…As well as our results, Bunraksa et al (2020) demonstrated a great diversity of microorganisms isolated in the poultry slaughterhouse sludge, and some microorganisms have the effect of synthesizing substances that promote growth in plants. Also reported a great diversity of bacteria isolated in poultry slaughterhouse sludge, some of which have the ability to fix atmospheric N (Lozada et al, 2018).…”