Scirpus americanus Pers. occurs naturally in “San Germán,” a pond that serves as a receptor of industrial wastewater in Guanajuato, México. This plant accumulates metals mainly in the root: concentrations (mg/kg) of Cr, As, Cd and Se were 970, 49, 41, and 85 respectively. Analysis of rhizosphere samples indicated bacterial population of 10⁸ cfu g⁻¹ in media with 0.2 mM Cr(VI) and 10 mM sodium gluconate. Thirteen isolates were obtained and phylogenetic analyses (16S rRNA) indicated they corresponded to genera of Agrobacterium, Arthrobacter, Microbacterium, Curtobacterium, Rhodococcus, Xanthomonas and Pseudomonas. Cr(VI) reduction was evaluated using the diphenyl carbazide method. The isolates accomplished 5–40% (20 μM) of reduction in assays of resting cell and tolerated 0.5–5.0 mM Cr(VI). Eight strains used nitrate and thirteen used iron and chromium as electron acceptors to grow under anaerobic conditions. Cr(VI) reduction by five strains occurred at pH values (7–9) and NaCl concentrations (0.5–1.0 M) in basal medium. A mixed culture of strains (S17 and S28) reached a chromium removal of 100% at 0.2 mM Cr(VI) initial concentration. Aerobically, this consortium was capable of 93.8% Cr(VI) reduction of 81 μgL⁻¹ Cr(VI) of the industrial effluent, indicating their possible use in environmental cleanup.

The diseases found in Pinus patula, a species present in the forest area of Puebla, Mexico cause foliage loss and damage to trees and we consider that fungi could be involved. The objective of the current investigation was to study the nutrients of the soil and the fungi associated with the lesions on the needles of Pinus patula in Tetela de Ocampo, Puebla, Mexico. It was found that the nitrogen, phosphorus and potassium content of the soils associated with pine, as well as the organic matter, were poor. In addition, we performed chemical, physical and biological analyses on soils from the study site. We isolated forty-five fungi from the lesions on the needles. The identification of twelve of them was both morphological and molecular by sequence analysis of the ITS1-ITS2 gene. The identified fungi included Alternaria alternata, Annulohypoxylon stygium, Botryosphaeria dothidea, Curvularia lunata, Curvularia pseudobrachyspora, Curvularia spicifera, Curvularia trifolii, Daldinia eschscholtzii, Daldinia sp. Diplodia sapinea, Lophodermium indianum and Myrmaecium rubricosum. We concluded that P. patula is affected by nutritional deficiency as well as by the presence of phytopathogenic fungi.

In Mexico, one of the principal natural resources is oil, however, the activity related to it has generated hydrocarbon spills on agricultural soils. The aim of this study was to evaluate the biodegradability of diesel by means of indigenous bacteria isolated from agricultural soil contaminated with 68 900 mg kg(-1) diesel. We examined indigenous bacterial strains in agricultural soils contaminated with diesel from Acatzingo, Puebla. Mexico. We performed a physicochemical soil characterization, and a bacterial population quantification favoring sporulated bacteria of the genera Bacillus and Paenibacillus taken from the study site. Six bacterial strains were isolated. The identification was made based on the 16S rRNA gene and API systems. The tolerance and biodegradation capacity in diesel were determined at 4 000 to 24 000 mg L-1 of diesel. Residual concentrations of diesel were determined by GC-FID. Soil contaminated with diesel alters the concentrations of organic matter, phosphorus and nitrogen. Analysis of soil samples showed heat resistant bacterial populations of 10(6) cfu g(-1) dry soil. Six strains from soil pollution were identified - Pseudomonas stutzeri M1CH1, Bacillus pumilus M1CH1b, Bacillus cereus M1CH10. Bacillus subtilis M1CH15a. and Paenibacillus lautus strains M1CH19 and M1CH27. These bacteria showed different degradation behavior. Bacillus pumilus M1HC1b and Paenibacillus lautus M1CH27 use diesel oil as the sole carbon source. Bacillus pumilus degraded high concentrations of diesel (24 000 mg L-1), while for Paenibacillus lautus it became toxic and the degradation was less.

In Acatzingo, Puebla, Mexico (east-central), oil spills have mainly affected agricultural fields. Pleurotus ostreatus is a white rot basidiomycete and produces extracellular enzymes (lacasses, manganese peroxidases, versatile peroxidases and veratryl alcohol oxidases). The production of edible mushrooms generates spent mushroom substrate that may have a biotechnological application. The aim of this study was to evaluate the mushroom substrate of P. ostreatus in a microcosm for the bioremediation of an agricultural soil contaminated with diesel. We evaluated the participation of microbial populations and specific enzymatic lacasses, manganese peroxidases, versatile peroxidases, veratryl alcohol oxidases activities of mushroom substrate in the biodegradation of a soil contaminated with 11030 ppm of diesel in four treatments: E1, E2, E3 and E4. All the experiments were performed in triplicate at 25 and 37°C for 28 days, with a soil:substrate ratio of 4:1. The treatments incubated at 37°C were quantified for diesel-tolerant bacteria, and treatments incubated at 25°C were quantified for diesel-tolerant fungi. Mushroom substrate participated in the biostimulation (91% organic material, 0.56% total nitrogen and 0.3% phosphorus) and bioaugmentation of the microorganisms of the mirocosm. Bacteria-tolerant populations increased significantly (p = 0.000) in all the treatments. Lacasses (8.62 U g-1) activity was stimulated at 25°C and was the only one related to biodegradation; however, the highest biodegradation rate (72%) was at 37°C (bacterial biodegradation) being promising for future research. Key words: Bioremediation, diesel, laccase, veratryl alcohol oxidase, Pleurotus ostreatus.

The cultivation systems of Coffea spp. in a cooperative society in Puebla, Mexico, include Rustic, Traditional Polyculture, Commercial Polyculture, Unshaded Monoculture and Shaded Monoculture. In this work, the properties of the soil were analyzed through physical, chemical and biological analyses to determine its nutritional status. Composite sample analyses were conducted to determine physical, chemical and microbiological parameters (fungi, actinomycetes, mesophilic bacteria, nitrifying and denitrifying bacteria). Leaf nutrients were determined. Rustic was the cropping system with the highest amount of K in the soil and nutrient assimilation in the leaf (N, P, K and Fe) (p = 0.001); in addition, it had high populations of mesophilic bacteria, fungi and actinomycetes and very low nitrification and denitrification rates. The principal component analyses (PCA) (>3.25%) indicated that actinomycetes and K in soil favor the assimilation of Fe, K and P. This Coffea spp. cultivation system generated a lower impact on soil health than the rest of the systems and favored forest ecosystem conservation.