In this study, five microalgal strains were isolated from Bahía de La Paz, Baja California Sur, Mexico and identified as Grammatophora sp., Navícula sp., Rhabdonema sp., Schizochytrium sp., and ...Nitzschia sp., and their evaluation as potential food for Artemia franciscana. The isolated strains were cultured outdoors and harvested after four days. Chaetoceros muelleri was cultured under laboratory conditions and used as control. The protein, lipid, and carbohydrate composition and the fatty acid profiles of the strains were determined by gas chromatography. To assess the effect of microalgal strains on A. franciscana, decapsulated cysts were cultured at outdoor conditions in 15 L containers. The experiment was conducted for twelve days. Samples from the five different feeding treatments were taken at the beginning and end of the experiment to assess number, size, and weight of Artemia larvae. Treatment with Rhabdonema sp. showed larvae with a lower percentage of polyunsaturated fatty acids (PUFAs) while Grammatophora sp. showed those with the greatest PUFA proportion, even more than those fed Chaetoceros muelleri (control). Larvae consuming Schizochytrium sp. had no docosahexanoic (DHA) nor eicosapentaenoic (EPA) fatty acid content. Growth and survival of A. franciscana did not show significant differences among feed treatments, except when it was fed Nitzschia sp., showing lower survival and dry weight. Treatment based on Schizochytrium sp. and Rhabdonema sp. had a greater A. franciscana size but reduced dry weight; additional tests including two or more algal species for every treatment should be carried out to determine the best yield.
This study examined the effect of potential probiotic bacteria on growth and survival of the tilapia Oreochromis niloticus, under high density and suboptimum temperature. Presumptive Bacillus and ...lactic acid bacteria (LAB) were isolated from tilapia and from their culture system and were characterized for haemolytic and enzymatic activity, and antagonism against Vibrio. Selected strains were included in the diet of juvenile tilapia and evaluated during a 134-day assay. The experiment was conducted with four treatments: (1) fish fed with commercial feed plus Dry Oil®; (2) fish fed with commercial feed plus LAB; (3) fish with bacilli in water; (4) fish with a mixture of treatments 2 and 3. Tilapias in all treatments, including bacteria, grew significantly better than fish fed with commercial feed plus Dry Oil® (control group). Survival was similar in all treatments. The physicochemical parameters of the culture system were maintained within the optimal ranges for the species, with the exception of temperature (19.9-24.82 °C). Animals fed diet supplemented with bacilli and LAB had good survival and the best growth performance, suggesting that bacteria are appropriate growth-stimulating additives in tilapia cultivation.
Knowledge regarding the diversity of methanogenic archaeal communities in hypersaline environments is limited because of the lack of efficient cultivation efforts as well as their low abundance and ...metabolic activities. In this study, we explored the microbial communities in hypersaline microbial mats. Bioinformatic analyses showed significant differences among the archaeal community structures for each studied site. Taxonomic assignment based on 16S rRNA and methyl coenzyme-M reductase (
gene sequences, as well as metagenomic analysis, corroborated the presence of Methanosarcinales. Furthermore, this study also provided evidence for the presence of Methanobacteriales, Methanomicrobiales, Methanomassiliicoccales,
Methanofastidiosales, Methanocellales, Methanococcales and Methanopyrales, although some of these were found in extremely low relative abundances. Several
environmental sequences were significantly different from those previously reported and did not match with any known methanogenic archaea, suggesting the presence of specific environmental clusters of methanogenic archaea in Guerrero Negro. Based on functional inference and the detection of specific genes in the metagenome, we hypothesised that all four methanogenic pathways were able to occur in these environments. This study allowed the detection of extremely low-abundance methanogenic archaea, which were highly diverse and with unknown physiology, evidencing the presence of all methanogenic metabolic pathways rather than the sheer existence of exclusively methylotrophic methanogenic archaea in hypersaline environments.
Biofloc systems in Pacific white shrimp (Penaeus vannamei) culture generate floccules that remove wastes, and hence, biofloc formation is promoted for shrimp production. This study evaluated the ...induction of biofloc formation using microalgae and probiotic bacteria in hyper-intensive Pacific white shrimp culture. The experiment was performed for six weeks in tanks (28,000 L each) stocked 350 ind m-3 and weight of 1400 ± 30 mg. Three treatments were assessed: 1) with two diatoms: Grammatophora sp. and Navicula sp., 2) with Navicula sp., and 3) without diatoms. All treatments were added with Schizochytrium sp. and Lactobacillus fermentum TD19. The following parameters were monitored during culture: ammonium, nitrites, nitrates, environmental variables, floccules volume, microorganism presence, the bromatological composition of biofloc, and growth performance parameters of P. vannamei. Our results indicated that the three induced biofloc presented a similar volume (8.34 ± 4.8 mL L-1) and ammonium concentration (<1.0 mg L-1). Treatment 1 generated floccules with the highest concentration of ciliates, rotifers, nematodes, lactic acid bacteria, and the lowest concentration of Vibrio spp. (1.2×103 UFC mL-1), evidencing a significant difference in bromatological composition, with the highest protein and lipid values (28.12 ± 0.50 and 22.44 ± 0.80% biofloc dry weight, respectively) and the best feed conversion ratio (0.89). Based on these results, we suggest that Schizochytrium sp., L. fermentum, and two diatoms should be used to induce biofloc in a hyper-intensive culture of P. vannmaei in order to provide a supplementary nutritional intake, which can constitute an advantage to reduce commercial feed rations.
One of the main problems in laboratories of oyster seed production occurs in the stage of settlement or fixation and metamorphosis of the larvae. The organisms develop drastic morphological and ...physiological changes at this stage, exposing them to attack by pathogenic microorganisms. Numerous studies indicate that before larval settlement to a substrate, they require bacteria to stimulate and induce the process. In this study, Japanese oyster (Crassostrea gigas) larvae were fed with combinations of microalgae and bacteria previously selected for their probiotic potential; their impact on survival, growth, and settlement was evaluated. Larvae D of 12 days old were provided by a private company and transported to the laboratory under controlled conditions. Probiotic bacteria Lactobacillus plantarum 69Cr, L. fermentum 101Cc, and L. casei 43Cg were reactivated on MRS and applied at a concentration of 1 X 10.sup.4 CFU mL.sup.-1. Microalgae Isochrysis galbana and Chaetoceros calcitrans were grown in F2 medium and supplied at a concentration of 3 X 10.sup.4 cells mL.sup.-1. Results showed, in all treatments, a survival range of 39-53%, growth of 300-310 microm, and 34-56.5% settlement. However, the best bacteria combined with I. galbana and C. calcitrans was L. plantarum 69Cr with a 54% survival, 310 microm growth, and 56.5% settlement. It is concluded that the combination of L. plantarum 69Cr with I. galbana and C. calcitrans has the potential to be used in the production of Japanese oyster larvae.
Biofloc systems in Pacific white shrimp (Penaeus vannamei) culture generate floccules that remove wastes, and hence, biofloc formation is promoted for shrimp production. This study evaluated the ...induction of biofloc formation using microalgae and probiotic bacteria in hyper-intensive Pacific white shrimp culture. The experiment was performed for six weeks in tanks (28,000 L each) stocked 350 ind m.sup.-3 and weight of 1400 + or - 30 mg. Three treatments were assessed: 1) with two diatoms: Grammatophora sp. and Navicula sp., 2) with Navicula sp., and 3) without diatoms. All treatments were added with Schizochytrium sp. and Lactobacillus fermentum TD19. The following parameters were monitored during culture: ammonium, nitrites, nitrates, environmental variables, floccules volume, microorganism presence, the bromatological composition of biofloc, and growth performance parameters of P. vannamei. Our results indicated that the three induced biofloc presented a similar volume (8.34 + or - 4.8 mL L.sup.-1) and ammonium concentration (<1.0 mg L.sup.-1). Treatment 1 generated floccules with the highest concentration of ciliates, rotifers, nematodes, lactic acid bacteria, and the lowest concentration of Vibrio spp. (1.2X10.sup.3 UFC mL.sup.-1), evidencing a significant difference in bromatological composition, with the highest protein and lipid values (28.12 + or - 0.50 and 22.44 + or - 0.80% biofloc dry weight, respectively) and the best feed conversion ratio (0.89). Based on these results, we suggest that Schizochytrium sp., L. fermentum, and two diatoms should be used to induce biofloc in a hyper-intensive culture of P. vannmaei in order to provide a supplementary nutritional intake, which can constitute an advantage to reduce commercial feed rations.
Las macroalgas marinas son un método de control biológico que disminuyen el daño que provoca el nematodo agallador en los cultivos de importancia económica. El presente estudio tuvo como objetivo ...evaluar el efecto de cuatro macroalgas en el control de Meloidogyne incognita y su efecto bioestimulante en albahaca. Para ello, cuatro extractos derivados de Ulva lactuca, Ulva clathrata, Gracilaria spp. y Sargassum spp. fueron evaluados en tres dosis (1 000, 2 000 y 3 000 ppm) sobre la eclosión de huevecillos y su eficacia en la germinación, longitud de tallo y raíz de plántulas. Se realizó un análisis fitoquimico de las macroalgas que presentaron acción nematicida sobre los huvecillos. Los resultados mostraron que el extracto de Sargassum spp. y U. lactuca bajo las dosis evaluadas generaron el menor número de huevecillos eclosionados. Pero, ninguna macroalga incrementó elporcentaje de germinación, pero si la longitud de tallo. El análisis fitoquímico del extracto de Sargassum spp. registró el mayor contenido de alcaloides, fenoles, fitoesteroles, péptidos y saponinas. Se comprueba la eficacia de algunas macroalgas marinas sobre el control de M. incognita y su acción bioestimulante en la planta, lo cual es de gran interés para la agricultura orgánica y convencional.
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