Agave tequilana Weber var. 'Azul' is grown for the production of tequila, inulin and syrup. Diverse bacteria inhabit plant tissues and play a crucial role for plant health and growth. In this study culturable endophytic bacteria were extracted from leaf bases of 100 healthy Agave tequilana plants. In plant tissue bacteria occurred at mean population densities of 3 million CFU/g of fresh plant tissue. Three hundred endophytic strains were isolated and 16s rDNA sequences grouped the bacteria into eight different taxa that shared high homology with other known sequences. Bacterial endophytes were identified as Acinectobacter sp., A. baumanii, A. bereziniae, Cronobacter sakazakii, Enterobacter hormaechei, Bacillus sp. Klebsiella oxytoca, Pseudomonas sp., Enterococcus casseliflavus, Leuconostoc mesenteroides subsp. mesenteroides and Gluconobacter oxydans. Isolates were confirmed to be plant growth promoting bacteria (PGPB) by their capacities for nitrogen fixation, auxin production, phosphate solubilization, or antagonism against Fusarium oxysporum AC132. E. casseliflavus JM47 and K. oxytoca JM26 secreted the highest concentrations of IAA. The endophyte Acinectobacter sp. JM58 exhibited the maximum values for nitrogen fixation and phosphate solubilization index (PSI). Inhibition of fungi was found in Pseudomonas sp. JM9p and K. oxytoca JM26. Bacterial endophytes show promise for use as bio-inoculants for agave cultivation. Use of endophytes to enhance cultivation of agave may be particularly important for plants produced by micropropagation techniques, where native endophytes may have been lost.

The chemical management of the black leaf streak disease in banana caused by Mycosphaerella fijiensis (Morelet) requires numerous applications of fungicides per year. However this has led to fungicide resistance in the field. The present study evaluated the activities of six fungicides against the mycelial growth by determination of EC50 values of strains collected from fields with different fungicide management programs: Rustic management (RM) without applications and Intensive management (IM) more than 25 fungicide application/year. Results showed a decreased sensitivity to all fungicides in isolates collected from IM. Means of EC50 values in mg L-1 for RM and IM were: 13.25 ± 18.24 and 51.58 ± 46.14 for azoxystrobin, 81.40 ± 56.50 and 1.8575 ± 2.11 for carbendazim, 1.225 ± 0.945 and 10.01 ± 8.55 for propiconazole, 220 ± 67.66 vs. 368 ± 62.76 for vinclozolin, 9.862 ± 3.24 and 54.5 ± 21.08 for fludioxonil, 49.2125 ± 34.11 and 112.25 ± 51.20 for mancozeb. A molecular analysis for β-tubulin revealed a mutation at codon 198 in these strains having an EC50 greater than 10 mg L-1 for carbendazim. Our data indicate a consistency between fungicide resistance and intensive chemical management in banana fields, however indicative values for resistance were also found in strains collected from rustic fields, suggesting that proximity among fields may be causing a fungus interchange, where rustic fields are breeding grounds for development of resistant strains. Urgent actions are required in order to avoid fungicide resistance in Mexican populations of M. fijiensis due to fungicide management practices.

Deteriorated limestone from Mayan buildings in Yucatan, Mexico, was analyzed with scanning electron microscopy (SEM) and microprobe with energy dispersive X-ray analysis (EDAX), X-ray diffraction (XRD) and Fourier-Transformed Infrared Spectroscopy (FTIR). Changes in surface chemical composition, caused by the biofilm layer and the conversion of calcite into gypsum, were demonstrated. Representative fungi include Aspergillus, Penicillium, Fusarium and Paecilomyces. Strains of Aspergillus niger and Penicillium sp., were selected for their ability to produce acidic metabolites. Both fungi excreted organic acids when incubated; ion exchange chromatography identified these acids as gluconic, succcinic-malic (coeluted) and oxalic. A. niger, the most active acid producer, also excreted citric acid. When grown in the presence of limestone coupons, calcium release from the mineral matrix paralleled the production of oxalic acid. However free calcium was considerably lower in filtrates from limestone coupon-containing culture, suggesting its complexation. SEM and EDAX confirmed that calcium oxalate crystals developed on the surface of the stone coupons. The results show that organic-acid-producing fungi may contribute to the deterioration of limestone monuments.

La roca caliza deteriorada de monumentos mayas de Yucatán, México, fue analizada por medio de microscopia electrónica de barrido acoplada con análisis por rayos X retrodispersados (SEM-EDAX), difracción de rayos X (XRD) y espectroscopia infrarojo transformada de Fourier (FT-IR). Los cambios en la composición química de la superficie causadas por la biopelícula con la consecuente conversión de calcita a yeso, fueron demostrados. Los géneros más abundantes fueron Aspergillus, Penicillium, Fusarium y Paecilomyces. Cepas de Aspergillus niger y Penicillium sp., fueron seleccionadas por su capacidad de producir metabolitos ácidos. Ambos hongos excretaron ácidos orgánicos cuando fueron incubados (glucónico, succínico, málico y oxálico). A. niger fue el productor más activo y también excreto ácido cítrico. El impacto del hongo sobre los cupones liberó calcio de la matriz mineral asociado a la producción de acido oxálico. Sin embargo, el calcio soluble fue considerablemente bajo en los filtrados de cultivos que contenían los cupones de piedra, sugiriendo quelación. El análisis de SEM-EDAX confirmó el papel biodeteriorante de los ácidos micogénicos.

The chemical changes in barley-straw (BS), wheat-straw (WS) and vineyard-pruning (VP) substrates were determined during colonization of Lentinula edodes mycelia (during primordium development) in solid state fermentation. Primordia appeared 39-50 days after inoculation. VP appeared to promote early sporophore initiation. The concentration of hemicellulose in BS and VP decreased gradually from 25.5% to 15.6% and from 15.8% to 12.3%, respectively. However in WS, hemicellulose decreased from 27.2% to 9.5%. Lignin broke down continuously in BS and WS, with 31.8% and 34.4% degradation, respectively; higher than that of cellulose. During the pinning stage, the C:N ratio decreased in VP and BS, but not in WS. On all substrates the phenols decreased notably throughout the first week of mycelial growth. The time elapsed (days) to pinning was positively correlated with cellulose content (r=0.89), total sugar (r=0.85) and inversely correlated to lignin (r=-1.00) and phenol content (r=-0.55).

Milled corn stalk (crude) was cleaned by diverse solvents (cleaned). When 1000 ppm of cleaned was added to Peptone / Glucose / Agar (PGA), the growth rate of Pleurotus ostreatus and Pleurotus sajor-caju was doubled. The mycelial diameter also increased by a supplementation of a hot water extract of cleaned corresponding to 1000 ppm, which was composed of 400 µg / g-stalk of nonvolatile compounds including 60 µg / g-stalk of phenolic monomers. An IR spectrum of the extract was very similar to that of cleaned and commercial lignin. Supplementation of crude or cleaned to Malt extract / Sucrose / Agar (MSA) promoted mycelial growth by 30 % in all five basidiomycete studied. A commercially available Kraft lignin supplemented to MSA showed cleaned-like growth promotions. The hot water extract showed growth promotion to the mycelia at a range of 10−6−10−7 M as seen in plant hormones. Therefore, we suggest these fungi use the enzymatic degradation products of lignin as a signal to faster mode of growth. This must be an important tactic of the fungi in securing their niche by degrading a vegetal biomass before competitors encroach upon it.

Tallos de maíz secos y molidos (crude) fueron lavados por varios solventes (cleaned). Cuando se añadió 1000 ppm de tallos lavados al medio de cultivo Peptona / Glucosa/ Agar (PGA), el crecimiento de Pleurotus ostreatus y Pleurotus sajor-caju se incrementó al doble. El crecimiento del micelio también aumenta cuando se añaden 1000 ppm de un extracto acuoso de tallos lavados (cleaned) compuesto de 400 µg de sustancias no volátiles por gramo de tallo. Este extracto contenía 60 µg / g de tallo de monómeros fenólicos. El análisis por IR muestra que el espectro del extracto es similar al de cleaned así como al de la lignina comercial. El crecimiento del micelio de 5 basidiomicetos se promovió en un 30 % al añadir crude y cleaned al medio de cultivo. El incremento en el crecimiento también ocurrió cuando se adicionó la lignina comercial al medio de cultivo de Agar Extracto de Malta. Este incremento fue similar al inducido por cleaned. El extracto acuoso incrementó el crecimiento en un intervalo de concentración de 10−6 a 10−7 M, tal y como se observa en las plantas cuando se les añade hormonas. Sugerimos que estos hongos basidiomicetos usan a los productos de la degradación enzimática de la lignina como una señal para acelerar su crecimiento. Este hecho puede ser una táctica importante de los hongos para degradar la biomasa vegetal antes que sus posibles competidores.