Effects of oil substrate supplementation on production of prodigiosin by Serratia nematodiphila for dye-sensitized solar cell.

Bacterial pigments are potential substitute of chemical photosensitizer for dye-sensitized solar cell (DSSC) due to its non-toxic property and cost-effective production from microbial fermentation. Serratia nematodiphila YO1 was isolated from waterfall in Malaysia and identified using 16S ribosomal RNA. Characterization of the red pigment produced by the bacteria has confirmed the pigment as prodigiosin. Prodigiosin was produced from the fermentation of the bacteria in the presence of different oil substrates. Palm oil exhibited the best performance of cell growth and equivalent prodigiosin yield compared to olive oil and peanut oil. Prodigiosin produced with palm oil supplementation was 93 mg/l compared to 7.8 mg/l produced without supplementation, which recorded 11.9 times improvement. Specific growth rate of the cells improved 1.4 times when palm oil was supplemented in the medium. The prodigiosin pigment produced showed comparable performance as a DSSC sensitizer by displaying an open circuit voltage of 336.1 mV and a maximum short circuit current of 0.098 mV/cm2. This study stands a novelty in proving that the production of prodigiosin is favorable in the presence of palm oil substrate with high saturated fat content, which has not been studied before. This is also among the first bacterial prodigiosin tested as photosensitizer for DSSC application.

Toxicity effects of Eriocephalus africanus L. leaf essential oil against some molecularly identified phytopathogenic bacterial strains.

Essential oil (EO) from Eriocephalus africanus L. leaves was evaluated against the growth of some phytopathogenic bacteria including Agrobacerium tumifaciens, Dickeya solani, Erwinia amylovora, Pseudomonas cichorii and Serratia pulmithica using the disc diffusion method and minimum inhibitory concentration (MIC) evaluation. Ten compounds in the EO with dominance of Artemisia ketone (2,5,5-trimethyl-2,6-heptadien-4-one) (77.92%) and ledol (19.92%) were revealed. The antibacterial activity indicated efficacy of essential oil against majority of strains isolated. The most effective action was recorded against D. solani, by 7.5 and 10 µL of oil, with 18.33 mm and 100 µg/mL as zone inhibition and MIC, respectively, whereas the lowest activity was exhibited against P. cichorii (diameter inhibition = 6.66 mm at 10 µL of oil, MIC = 100 µg/mL). The strain S. pulmithica appears to be resistant to the oil when the activity is measured by 10 µL of oil but its growth inhibition was reported with a MIC of 100 µg/mL.

Uranium biomineralization induced by a metal tolerant Serratia strain under acid, alkaline and irradiated conditions.

It has become increasingly apparent that the environmental microorganisms residing in uranium (U) enriched sites offer the possibility of understanding the biological mechanisms catalyzing the processes important for uranium bioremediation. Here, we present the results of uranium biomineralization over a wide pH range by a metal tolerant Serratia sp. strain OT II 7 isolated from the subsurface soil of a U ore deposit at Domiasiat in India. The Serratia cells actively expressed acid and alkaline phosphatase enzymes which hydrolyzed differential amounts of phosphate from an organophosphate substrate in the presence of uranium between pH 5 to 9. These cells precipitated ∼91% uranium from aqueous solutions supplemented with 1 mM uranyl nitrate at pH 5 within 120 h. More rapid precipitation was observed at pH 7 and 9 wherein the cells removed ∼93-94% of uranium from solutions containing 1 mM uranyl carbonate within 24 h. The aqueous uranyl speciation prevalent under the studied pH conditions influenced the localization of crystalline uranyl phosphate precipitates, which in turn, impacted the cell viability to a great extent. Furthermore, the cells tolerated up to ∼1.6 kGy 60Co gamma radiation and their uranium precipitation abilities at pH 5, 7 and 9 were uncompromised even after exposure to a high dose of ionizing radiation. Overall, this study establishes the ecological adaptation of a natural strain like Serratia in a uranium enriched environment and corroborates its contribution towards uranium immobilization in contaminated subsurfaces through the formation of stable uranyl phosphate minerals over a wide pH range.

Cultivar and Metal-Specific Effects of Endophytic Bacteria in Helianthus tuberosus Exposed to Cd and Zn.

Plant growth promoting endophytic bacteria (PGPB) isolated from Brassica napus were inoculated in two cultivars of Helianthus tuberosus (VR and D19) growing on sand supplemented with 0.1 mM Cd or 1 mM Zn. Plant growth, concentrations of metals and thiobarbituric acid (TBA) reactive compounds were determined. Colonization of roots of H. tuberosus D19 by Pseudomonas sp. 262 was evaluated using confocal laser scanning microscopy. Pseudomonas sp. 228, Serratia sp. 246 and Pseudomonas sp. 262 significantly enhanced growth of H. tuberosus D19 exposed to Cd or Zn. Pseudomonas sp. 228 significantly increased Cd concentrations in roots. Serratia sp. 246, and Pseudomonas sp. 256 and 228 resulted in significantly decreased contents of TBA reactive compounds in roots of Zn exposed D19 plants. Growth improvement and decrease of metal-induced stress were more pronounced in D19 than in VR. Pseudomonas sp. 262-green fluorescent protein (GFP) colonized the root epidermis/exodermis and also inside root hairs, indicating that an endophytic interaction was established. H. tuberosus D19 inoculated with Pseudomonas sp. 228, Serratia sp. 246 and Pseudomonas sp. 262 holds promise for sustainable biomass production in combination with phytoremediation on Cd and Zn contaminated soils.

Effect of tea polyphenols on microbiological and biochemical quality of Collichthys fish ball.

BACKGROUND: Tea polyphenols (TP), as the most active constituents of tea, are considered natural food additives. This study examined the preservative properties of TP for Collichthys fish ball in well storage. Vacuum-packed Collichthys fish balls were treated with 0, 0.1, 0.15, 0.20, 0.25, and 0.30 g kg(-1) TP and stored at 0 °C for 17 days. RESULTS: Microbiological results were obtained using a biochemical test, API system kit, and 16S rDNA sequence analysis. Results confirmed that the dominant bacteria in Collichthys fish balls are the genera Serratia and Pseudomonas. Total viable counts dropped two orders of magnitude in Collichthys fish balls with 0.25 g kg(-1) TP compared with the control. The advantages of total volatile basic nitrogen value, 2-thiobarbituric acid value and texture value were clearly observed, whereas pH and whiteness value exhibited no significant decrease for the group treated with 0.25 g kg(-1) TP. More than 0.25 g kg(-1) TP added could retain excellent fish ball characteristics in terms of sensory assessment after 17 days. CONCLUSION: The shelf life of Collichthys fish balls supplemented with tea polyphenols can be prolonged for an additional 6 days in good condition at 0 °C storage.

Increasing resistance in community-acquired urinary tract infections in Latin America, five years after the implementation of national therapeutic guidelines.

BACKGROUND: The worldwide increasing resistance to antibiotics has complicated antimicrobial treatment of urinary tract infections (UTIs), especially in Latin America. This study aimed to report the present etiology and antimicrobial susceptibility of UTIs, and the effects of the national guidelines for UTIs introduced in 2003. METHODS: Urine samples were collected from 304 patients with a clinical suspicion of UTI at the university hospital and primary health centers of León, Nicaragua. When bacterial growth was reported, antimicrobial susceptibility tests for nine frequently used antibiotics were performed. RESULTS: Ninety-one (29.9%) patients had a positive urine culture. The most frequently isolated microorganisms were Escherichia coli (n=44), Serratia spp (n=11), and Escherichia fergusonii (n=10). High resistance rates were observed in E. coli to ampicillin (61.4%), cefalothin (45.5%), trimethoprim-sulfamethoxazole (38.6%), ciprofloxacin (31.8%), and ceftriaxone (20.5%). Amikacin and nitrofurantoin were the only drugs to which >90% of E. coli were susceptible. E. fergusonii and Serratia spp showed comparable high resistance patterns. Thirteen strains (29.5%) of E. coli were suspected to produce extended-spectrum beta-lactamase (ESBL). CONCLUSIONS: Resistance rates in community-acquired UTIs in Nicaragua are increasing. The introduction of therapeutic guidelines with ceftriaxone recommended for upper UTIs and nitrofurantoin for lower UTIs, has led to increasing resistance against both antibiotics. The emergence of ESBL-producing E. coli is worrisome, along with the appearance of Serratia spp in the population.

Eremophilane-type sesquiterpene derivatives from Senecio aegyptius var. discoideus.

Investigation of a CH(2)Cl(2) extract of the aerial parts of Senecio aegyptius var. discoideus afforded nine eremophilane compounds, of which six are new (1-6), namely, 1beta-hydroxy-8alphaH-eremophil-7(11),9-dien-8beta,12-olide (1), 1beta,8alpha-dihydroxyeremophil-7(11),9-dien-8beta,12-olide (2), 1beta-hydroxy-8alpha-methoxyeremophil-7(11),9-dien-8beta,12-olide (3), 1-oxo-8alpha-methoxy-10alphaH-eremophil-7(11)-en-8beta,12-lactam (4), 1beta,10beta-epoxy-8alpha-hydroxyeremophil-7(11)-en-8beta,12-olide (5), and 1beta,10beta-epoxy-8alpha-methoxyeremophil-7(11)-en-8beta,12-olide (6). The structures of 1-6 were elucidated by spectroscopic methods and by comparison with literature data. The antibacterial activity of the isolated compounds was tested against Bacillus cereus and a Serratia sp.

The antimicrobial activity of Prevention mouthrinse.

Prevention mouthrinse was designed to serve as a vital supplement to normal oral hygiene procedures. To determine the antimicrobial potency of this mouthrinse, minimal inhibitory concentrations (MICs), bactericidal kinetics, and short-term exposure studies were conducted. A spectrum of oral microorganisms was employed in this investigation: Streptococcus sanguis, Streptococcus anginosus, Streptococcus mutans, Actinomyces viscosus, Actinobacillus actinomycetemcomitans, Fusobacterium nucleatum, Eikenella corrodens, Porphyromonas gingivalis, Serratia marcescens and Candida albicans. Microorganisms were cultured in standard enriched media and under appropriate atmospheric conditions. Inhibition assays were conducted in tubes, with each mouthrinse dilution assayed in triplicate. MIC determinations revealed that all of the microorganisms studied were highly susceptible to Prevention mouthrinse, with MICs ranging from 16-fold to 128-fold dilutions. Bactericidal kinetics assays showed rapid killing of the test organisms in the presence of the mouthrinse. Brief (5-minute) exposure of S. mutans to 8-fold diluted mouthrinse resulted in a substantial delay in growth. Under the constraints of this type of study, Prevention mouthrinse exhibited potent antimicrobial activity against all of the microorganisms studied. We support the notion that Prevention mouthrinse may be a valuable supplement to normal oral hygiene procedures. A 6-month clinical trial assessing the in vivo efficacy of Prevention mouthrinse is currently being conducted.

In vitro antibacterial activity of norfloxacin compared with eight other antimicrobial agents.

The antibacterial activity of norfloxacin, an organic acid structurally related to nalidixic acid, was compared with that of the oral cephalosporins cefaclor and cephalexin, and with that of nalidixic acid, cinoxacin, amikacin, ampicillin, trimethoprim alone and the combination of trimethoprim and sulfamethoxazole. Agar dilution studies were performed with a total of 398 clinical isolates of gram-negative bacteria. Norfloxacin was found to be the most active drug studied against each of the different groups of organisms tested. MIC90 values for norfloxacin were as follows: Citrobacter spp., 2 micrograms/ml; Enterobacter spp., 0.13 micrograms/ml; Escherichia coli, 0.06 micrograms/ml; Klebsiella spp., 0.13 micrograms/ml; Proteus spp., 0.06 micrograms/ml; Salmonella spp., 1 microgram/ml; Serratia spp., 0.13 micrograms/ml; and Pseudomonas spp., 2 micrograms/ml. MIC90 values for the other drugs were 4 micrograms/ml or greater and many organisms were totally resistant to one or more of the other drugs (MIC greater than 128 micrograms/ml). Cross resistance between norfloxacin and the related drugs nalidixic acid and cinoxacin was not observed.

[Evolution of the intestinal flora in patients under preventive treatment with cephalosporins]. / Evolution de flores intestinales de patients traités à titre prophylactique par des céphalosporines.

The evolution of the intestinal flora has been studied in 20 patients undergoing chemoprophylaxis with cephalosporins. The patients, admitted to the Cantonal Hospital of Geneva for heart surgery, all received intravenous treatment initiated on the day of admission. Subsequently, one group continued to receive a cephalosporin orally while prophylaxis was discontinued in a second group. Microbiological analysis of aerobic bacteria in faeces demonstrated in both groups (1) a significant increase in resistance to beta-lactamines (ampicillin); (2) a parallel though lesser increase in resistance to other antibiotics (which shows the probable role of plasmids carrying drug resistance markers); and (3) an increase in bacteria known for their resistance to beta-lactamines (klebsiella, enterobacter, pseudomonas). These results demonstrate that a single intravenous administration of beta-lactamines has a selective effect on the intestinal flora and notably on bacteria which are known to be the cause of infectious diseases acquired in hospitals.

Toxic effect of water-soluble fractions of crude, refined, and weathered oils on the growth of a marine bacterium.

The water-soluble fractions of three crude and two refined oils reduced the growth rate and maximum cell density of the marine bacterium Serratia marinorubra grown in batch culture. The weathering of a crude and a refined oil was simulated in the laboratory. The water-soluble fractions remaining from this process were more toxic to S. marinorubra than were the parent unweathered oils. Increases in the magnitude of toxic effect of 3 to 30 times were observed as a function of decreasing the concentration of yeast extract in the cultures from 0.1 to 0.05 and 0.01%. The toxicity did not correlate with the concentration of total water-soluble fraction or of aromatic hydrocarbons in the water-soluble fraction. Affected cultures did not exhibit a residual toxicity after being back-inoculated into control media.