Stimulation of sulfate reduction rates in Mediterranean fish farm sediments inhabited by the seagrass <Emphasis Type="Italic">Posidonia oceanica</Emphasis>

Sulfate reduction rates and biogeochemical parameters of fish farm sediments across the Mediterranean were investigated in the order to evaluate the potential effects of organic matter inputs on habitat quality for the common seagrass Posidonia oceanica. Four study sites were selected in Spain, Italy, Greece and Cyprus to represent the Mediterranean basin. P. oceanica was found in immediate vicinity of all the farms, which were located at physically exposed sites about 1 km from the shore lines. Organic matter accumulation, sulfate reduction rates and sulfur pools were measured in depth profiles along transects from the farms in both bare and vegetated sediments. Results show that although the organic matter accumulation was minor at the sites (POC < 2.8% DW), the sulfate reduction rates were high, in particular at the largest farm in Italy (up to 212 mmol m⁻² d⁻¹), similar to rates found at shallower, temperate fish farm sites, where higher sedimentation rates can be expected. Sulfate reducing bacteria in these low-organic, carbonate-rich Mediterranean sediments respond strongly to organic matter loadings and cause habitat degradation. Sulfate reduction rates measured in the P. oceanica sediments were among the highest recorded (7.8–42.0 mmol m⁻² d⁻¹) similar to rates found in degrading meadows impacted by organic matter loadings. As sulfate reduction rates were correlated with the sedimentation rates along the transects rather than organic matter pools this suggests mineralization processes were controlled by organic matter loading in fish farm sediments. The vegetated sediments near the net cages were more reduced due to accumulation of sulfides compared to control sites, which is a possible contributing factor to the observed seagrass decline in the farm surroundings. It is recommended that Mediterranean fish farms are placed in areas with rapid dispersal of particulate waste products to minimize organic matter loading of the sediments and thereby preserve habitat quality for benthic fauna and flora.     

Taxonomic composition of bacteria associated with cultivated mollusks <Emphasis Type="Italic">Crassostrea lugubris</Emphasis> and <Emphasis Type="Italic">Perna viridis</Emphasis> and with the water of the Gulf of Nha Trang lagoon,Vietnam

One hundred and four strains of heterotrophic bacteria have been isolated and characterized from two species of bivalve mollusks cultivated in the Gulf of Nha Trang (Vietnam) and from the water of a mariculture farm. The isolates have been identified on the basis of morphological, physiological, biochemical, and chemotaxonomic properties, as well as by the content of G+C bases in DNA. In the microflora of mollusks, Vibrio alginolyticus was predominant; the pathogenic species V. harveyi and V. splendidus were found as well. Staphylococci and bacilli occupied the second place in abundance after vibrios. In addition, coryneforms and enterobacteria, as well as Pseudomonas spp. and Pseudoalteromonas spp., were revealed. The composition of the water microflora was more diverse as compared with the microflora of mollusks. In the water, Bacillus spp., Vibrio spp., and Pseudomonas spp. were predominant. Brevibacterium spp. and other coryneform bacteria, as well as enterobacteria, occurred in significant amounts. In addition, Pseudoalteromonas spp., Marinococcus sp., Halobacillus sp., Shewanella sp., Sulfitobacter sp., and bacteria of the CFB cluster were noticed. The presence of pathogenic and conditionally pathogenic bacterial species in the water and mollusks is probably the reason for the high death rate of cultivated animals at the mariculture farm.     

Conjugated linoleic acid conversion by dairy bacteria cultured in MRS broth and buffalo milk

AIMS: To evaluate strains of Lactobacilli, Bifidobacteria and Streptococci for their ability to produce conjugated linoleic acid (CLA) from free linoleic acid (LA). METHODS AND RESULTS: Eight dairy bacteria tolerant to LA were grown in MRS broth containing LA (200 microg ml(-1)) and CLA was assessed. Seven bacteria were able to form CLA after 24 h of incubation, varying percentage conversion between 17% and 36%. Lactobacillus casei, Lactobacillus rhamnosus, Bifidobacterium bifidum and Streptococcus thermophilus showed the highest LA conversion and were inoculated into buffalo milk supplemented with different concentration of LA. The production of CLA at 200 microg ml(-1) of LA was two- or threefold in milk than MRS broth. All evaluated strains were able to produce CLA from high LA levels (1000 microg ml(-1)). CONCLUSIONS: The most tolerant strain to LA was Lact. casei. Lacttobacillus rhamnosus produced the maximum level of CLA at high LA concentrations (800 microg ml(-1)). The selected bacteria may be considered as adjunct cultures to be included on dairy fermented products manufacture. Low concentration of LA must be added to the medium to enhance CLA formation. SIGNIFICANCE AND IMPACT OF THE STUDY: The production of CLA by strains using milks from regional farms as medium offer a possible mechanism to enhance this beneficial compound in dairy products and those the possibility to develop functional foods.     

Phenotypical characteristics of Shiga-like toxin Escherichia coli isolated from sheep dairy products

AIMS: To analyse phenotypical characteristics of Shiga toxin-producing Escherichia coli (STEC) strains from ovine origin. METHODS AND RESULTS: A total of 13 STEC strains (eight O157 and five non-O157) isolated from sheep dairy products were used in this study. Biochemical traits, motility, haemolytic activity, resistance to tellurite-cefixime, maximum growth temperature and antibiotic resistance were determined. The STEC strains were grouped into nine biochemical and physiological biotypes (five for the O157 and four for the non-O157 strains). All STEC strains showed resistance to bacitracin, cloxacilin, penicillin and tylosin. CONCLUSIONS: Different biotypes and antibiotic resistance patterns of STEC isolated from sheep dairy products were observed. SIGNIFICANCE AND IMPACT OF THE STUDY: This work will be a contribution to the better characterization of STEC isolated from sheep dairy products, which have, to date, been scarcely studied, and to the better understanding of the risks associated with its consumption.     

<Emphasis Type="Italic">Daphnia galeata</Emphasis> in the deep hypolimnion: spatial differentiation of a “typical epilimnetic” species

One of the most serious threats to tropical mangrove ecosystems caused by shrimp farming activities is the poor management of pond waste materials. We hypothesise that mangroves can tolerate chemical residues discharged from shrimp farms and can be used as biofilters, but the capability of mangroves to cope with solid sediments dredged from shrimp ponds is limited. Our study in Pak Phanang, Thailand, confirmed that the excess sediments discharged from nearby shrimp ponds reduced mangrove growth rates and increased mortality rates. A series of transformed multi-temporal satellite images was used in combination with the field data to support this claim. In addition, a comparison between four dominant mangrove species revealed that Avicennia marina could tolerate sedimentation rates of >6 cm year⁻¹, while Bruguiera cylindrica tolerated sedimentation rates of 5 cm year⁻¹ (total sediment depth = 25 cm) before dying, while Excoecaria agallocha and Lumnitzera racemosa performed intermediate. This outcome implied that in our situation A. marina and to lesser extent E. agallocha and L. racemosa could be more effective as biofilters than B. cylindrica, as they may survive the sedimentation longer in the disposal areas. Further studies on the impact of sedimentation and chemical pollution of shrimp farm wastes on mangrove mortality and growth are required.     

Enzymatic pre-hydrolysis applied to the anaerobic treatment of effluents from poultry slaughterhouses

A pool of hydrolases with 21.4 U g⁻¹ lipase activity was produced through solid-state fermentation of the fungus Penicillium restrictum in waste from the Orbignya oleifera (babassu) oil processing industry. Enzymatic hydrolysis and anaerobic biodegradability tests were conducted on poultry slaughterhouse effluents with varying oil and grease contents (150–1200 mg l⁻¹) and solid enzymatic pool concentrations (0.1–1.0% w/v). Enhanced anaerobic treatment efficiency relative to raw effluent was achieved when a 0.1% concentration of enzymatic pool was used in the pre-hydrolysis stage with 1200 mg oil and grease l⁻¹ (chemical oxygen demand (COD) removal efficiency of 85% vs. 53% and biogas production of 175 ml vs. 37 ml after 4 d).     

Characterization of dominant lactic acid bacteria isolated from São Jorge cheese, using biochemical and ribotyping methods

Aims: To identify, using phenotypic and genotypic methods, the dominant lactic acid bacteria (LAB) present in São Jorge cheese – one of the 11 Portuguese cheeses currently bearing an Appéllation d’Origine Protegée status. Methods and Results: A total of 225 isolates from milk, curd and cheeses throughout ripening were identified to the genus level, 108 to the species level and ten to the strain level. Phenotypic methods indicated that lactobacilli, followed by enterococci, were the dominant bacteria. The most frequently isolated species were Lactobacillus paracasei, Lactobacillus rhamnosus, Enterococcus faecalis and Enterococcus faecium. Ribotyping differentiated three L. paracasei, two E. faecalis and one Lactobacillus plantarum types. Enterococcus spp. exhibited the highest esterase and β-galactosidase activities among all isolates. Conclusions: The dominant LAB in São Jorge cheese are L. paracasei, L. rhamnosus, E. faecalis and E. faecium. Enterococcus likely plays a leading role upon acidification and aroma development in said cheese. Significance and Impact of the Study:  Our results support that a combination of conventional biochemical methods with genotypic methods allows for a thorough characterization and identification of isolates. Despite the limited number of isolates subject to molecular subtyping, a few specific Enterococcus and Lactobacillus strains were found that are promising ones for development of a starter culture. Hence, L. paracasei and E. faecalis are good candidates for a tentative starter culture, designed for manufacturing of São Jorge cheese at large – which takes advantage of actual isolates, in attempts to eventually standardize the quality of said cheese variety.     

Characterization and performance of constructed nitrifying biofilms during nitrogen bioremediation of a wastewater effluent

Constructed ammonium oxidizing biofilms (CAOB) and constructed nitrite oxidizing biofilms (CNOB) were characterized during the bioremediation of a wastewater effluent. The maximum ammonium removal rate and removal efficiency in CAOB was 322 mg N-NH₄⁺ m⁻³ d⁻¹ and 96%, respectively, while in CNOB a maximum removal rate of 255 mg N-NH₄⁺ m⁻³ d⁻¹ and a removal efficiency of 76% was achieved. Both constructed biofilms on low-density polyester Dacron support achieved removal efficiencies higher than that of the concentrations normally present in reactors without constructed biofilms (P < 0.05). Nitrifying bacteria from the constructed biofilms cultures were typed by sequencing 16S rRNA genes that had been amplified by PCR from genomic DNA. Analysis of enrichment biofilms has therefore provided evidence of high removal of ammonium and the presence of Nitrosomonas eutropha, N. halophila and N. europaea in CAOB, while in CNOB Nitrobacter hamburgensis, N. winogradskyi and N. alkalicus were identified according to 16S rRNA gene sequences comparison. The biofilm reactors were nitrifying over the whole experimental period (15 days), showing a definite advantage of constructed biofilms for enhancing a high biomass concentration as evidenced by environmental electron microscopic analysis (ESEM). Our research demonstrates that low-density polyester Dacron can be effectively used for the construction of nitrifying biofilms obtaining high removal efficiencies of nitrogen in a relatively short time from municipal effluents from wastewater treatment plants. CAOB and CNOB are potentially promissory for the treatment of industrial wastewaters that otherwise requires very large and expensive reactors for efficient bioremediation of effluents.     

Prevalence and antimicrobial resistance of Campylobacter in US dairy cattle

AIMS: To obtain an overview of the prevalence and antimicrobial resistance of Campylobacter in faeces of US dairy cows in 2002. METHODS AND RESULTS: Faeces from 1435 cows, representing 96 dairy operations in 21 US states, were collected for the culture of Campylobacter. A total of 735 Campylobacter strains were isolated (51.2% positive samples) with 94 operations positive (97.9%) for Campylobacter. From this collection, 532 isolates (473 Campylobacter jejuni and 59 Campylobacter coli) were randomly selected for susceptibility testing to eight antimicrobials: azithromycin, chloramphenicol, ciprofloxacin, clindamycin, erythromycin, gentamicin, nalidixic acid and tetracycline. The C. jejuni isolates exhibited resistance to tetracycline (47.4%), nalidixic acid (4.0%) and ciprofloxacin (2.5%), while the C. coli strains exhibited some resistance to all antimicrobials except chloramphenicol and ciprofloxacin. Only 3.6% of the C. jejuni isolates were resistant to two or more antimicrobials but 20.3% of the C. coli strains were multiresistant. CONCLUSIONS: On most operations, at least one cow was positive for Campylobacter and more than half of the cows sampled were shedding Campylobacter. The C. coli isolates had significantly higher levels of resistance to macrolides and to tetracycline compared with the C. jejuni strains, but were susceptible to ciprofloxacin. SIGNIFICANCE AND IMPACT OF THE STUDY: This study demonstrated a high prevalence of Campylobacter on US dairy operations; however, US dairy cattle have not been recognized as a major source of human infection compared with poultry. Campylobacter coli appears to develop antimicrobial resistance more readily than C. jejuni from the same environment.     

青羊湖林场不同林分物种多样性与水源涵养能力的研究

通过群落调查和林下土壤及枯落物特性的分析,研究了青羊湖林场南酸枣（Choerospondias axillaris）林、未抚育马尾松（Pinus massoniana）林、抚育马尾松林、马尾松-南酸枣混交林4种林分的物种多样性及水源涵养能力。结果表明：（1）4种林分共有维管束植物135种,隶属58科97属,其中南酸枣林物种相对较丰富(88种),混交林次之(76种),抚育马尾松林较少(64种),未抚育马尾松林则相对最少(55种);（2）林分类型对物种多样性有重要影响,南酸枣林和混交林草本物种多样性较两种针叶林高,而灌木物种多样性则较低;（3）DCA排序结果显示,南酸枣林和混交林物种相似性程度较高,两种马尾松林与南酸枣林、混交林差异明显;（4）林分类型对水源涵养能力有重要影响,相比两种马尾松林,南酸枣林和混交林的林下枯落物蓄积量分别降低10.1%和15.2%,最大持水量降低34.1%和44.7%,而且0～10 cm土壤容重降低14.7%和7.4%,10～20 cm土壤容重降低14.1%和4.0%,20～30 cm土壤容重降低8.7%和4.9%,但总储水量增加15.8%和4.5%,即南酸枣林和混交林具有较高的水源涵养能力。研究认为,生态抚育增加了马尾松林的水源涵养能力。