The excessive use of fertilizers in agriculture is mainly due to the recognized plant requirements for soluble phosphorus. This problem has limited the implementation of sustainable agriculture. A viable alternative is to use phosphate solubilizing soil microorganisms. This work aimed to isolate inorganic phosphorus-solubilizing bacteria from the soils of agroecosystems, to select and identify, based on sequencing and phylogenetic analysis of the 16S rRNA gene, the bacterium with the highest capacity for in vitro solubilization of inorganic phosphate. Additionally, we aimed to determine its primary phosphate solubilizing mechanisms and to evaluate its effect on Habanero pepper seedlings growth. A total of 21 bacterial strains were isolated by their activity on Pikovskaya agar. Of these, strain ITCB-09 exhibited the highest ability to solubilize inorganic phosphate (865.98 µg/mL) through the production of organic acids. This strain produced extracellular polymeric substances and siderophores that have ecological implications for phosphate solubilization. 16S rRNA gene sequence analysis revealed that strain ITCB-09 belongs to the genus Enterobacter. Enterobacter sp. ITCB-09, especially when immobilized in beads, had a positive effect on Capsicum chinense Jacq. seedling growth, indicating its potential as a biofertilizer.

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Cadmium is a major heavy metal found in polluted aquatic environments, mainly derived from industrial production processes. We evaluated the biosorption of solubilized Cd2+ using the extracellular polymeric substances (EPS) produced by Bacillus sp. MC3B-22 and Microbacterium sp. MC3B-10 (Microbactan); these bacteria were originally isolated from intertidal biofilms off the coast of Campeche, Mexico. EPS were incubated with different concentrations of cadmium in ultrapure water. Residual Cd2+ concentrations were determined by Inductive Coupled Plasma-Optic Emission Spectrometry and the maximum sorption capacity (Qmax) was calculated according to the Langmuir model. EPS were characterized by X-ray photoelectron spectroscopy (XPS) before and after sorption. The Qmax of Cd2+ was 97 mg g−1 for Microbactan and 141 mg g−1 for MC3B-22 EPS, these adsorption levels being significantly higher than previously reported for other microbial EPS. In addition, XPS analysis revealed changes in structure of EPS after biosorption and showed that amino functional groups contributed to the binding of Cd2+, unlike other studies that show the carbohydrate fraction is responsible for this activity. This work expands the current view of bacterial species capable of synthesizing EPS with biosorbent potential for cadmium and provides evidence that different chemical moieties, other than carbohydrates, participate in this process.

The seaweed Sargassum (Sargassaceae) as tropical alternative for goats' feeding. The nutritive value of seaweed (Sargassum spp.) was studied in Baja California Sur, Mexico. Twenty female Nubian goats (43-weeks old) were randomly distributed into two groups of 10 goats each and were housed in individual pens. One group was fed with a control diet and the other with a diet supplemented with 25% of Sargassum spp. Feed and water intake were recorded daily and individually for 60 days. The weight of each goat was recorded every 15 days. The nutritional content of Sargassum spp. was 89% dry mater, 8% crude protein, 31% ash, 2% ether extract, and 39% carbohydrates. Fiber fractions, minerals, vitamins, fatty acids, and antinutritional factors were also determined. There were no significant differences in body weight (8.6 kg control and 9 kg experimental), feed intake (1.3 kg control and 1.6 kg experimental), and feed conversion rate (11.1 control and 12.6 experimental). Water consumption was greater in the goats that ate the Sargassum diet (5.3 l). From these results, Sargassum spp. can be considered as an alternative feedstuff for goats. Rev. Biol. Trop. 54(1): 83-92. Epub 2006 Mar 31.