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1.
《Veterinary microbiology》2015,175(1):105-113
Bacterial infections causing mastitis in sheep can result in severe economic losses for farmers. A large survey of milk samples from ewes with mastitis in Sardinia, Italy, indicated an increasing prevalence of Pseudomonas aeruginosa infections. It has been shown previously that during chronic, biofilm-associated infections P. aeruginosa populations diversify. We report the phenotypic and genomic characterisation of two clonal P. aeruginosa isolates (PSE305 and PSE306) from a mastitis infection outbreak, representing distinct colony morphology variants. In addition to pigment production, PSE305 and PSE306 differed in phenotypic characteristics including biofilm formation, utilisation of various carbon and nitrogen sources, twitching motility. We found higher levels of expression of genes associated with biofilm formation (pelB) and twitching motility (flgD) in PSE305, compared to the biofilm and twitching-defective PSE306. Comparative genomics analysis revealed single nucleotide polymorphisms (SNPs) and minor insertion/deletion variations between PSE305 and PSE306, including a SNP mutation in the pilP gene of PSE306. By introducing a wild-type pilP gene we were able to partially complement the defective twitching motility of PSE306. There were also three larger regions of difference between the two genomes, indicating genomic instability. Hence, we have demonstrated that P. aeruginosa population divergence can occur during an outbreak of mastitis, leading to significant variations in phenotype and genotype, and resembling the behaviour of P. aeruginosa during chronic biofilm-associated infections.  相似文献   
2.
《Veterinary microbiology》2015,175(1):114-122
Mannheimia haemolytica is the primary bacterial agent in the bovine respiratory disease complex. It is thought that M. haemolytica colonizes the tonsillar crypts of cattle as a commensal and subsequently descends into the lungs to cause disease. Many bacterial species persist in the host as biofilms. There is limited information about the ability of M. haemolytica to form biofilms. The aim of this study was to develop an in vitro model for M. haemolytica biofilm formation. We found that M. haemolytica required at least 36 h to form robust biofilms on plastic in vitro when incubated in RPMI-1640 tissue culture medium at 37 °C, with maximal biofilm formation being evident at 48 h. Biofilm formation was inhibited by adding the monosaccharides d(+) galactose and d(+) mannose to the growth medium. Addition of antibodies to the M. haemolytica surface protein OmpA also reduced biofilm formation. Upon evaluating the macromolecules within the biofilm extracellular polymeric substance we found it contained 9.7 μg/cm2 of protein, 0.81 μg/cm2 of total carbohydrate, and 0.47 μg/cm2 of extracellular DNA. Furthermore, proteinase K treatment significantly decreased biofilms (P < 0.05) while α-amylase and micrococcal nuclease decreased biofilms to a lesser extent. M. haemolytica biofilm cells were more resistant than planktonic cells to the antibiotics florfenicol, gentamicin, and tulathromycin. These results provide evidence that M. haemolytica can form biofilms, which could contribute to its ability to persist as a commensal in the bovine upper respiratory tract.  相似文献   
3.
The impact of temperature on nitrification rate in fixed film biofilters   总被引:12,自引:0,他引:12  
The impact of temperature on nitrification rate was evaluated in this study through experimental tests, mathematical modeling and sensitivity analysis. The results show that the impact of temperature on fixed film nitrification rate is less significant than that predicted by the van't Hoff–Arrhenius equation. In a fixed film biofilter, the impact of temperature on nitrification rate due to DO (dissolved oxygen) limitation is different from that due to TAN (total ammonia nitrogen) limitation. Sensitivity analysis indicated that a temperature increment at 20 °C resulted in nitrification rate increase of 1.108% per °C and 4.275% per °C under DO and TAN limited conditions, respectively. Diffusion mass transport plays an important role in fixed film nitrification processes. Consequently, the effect of temperature on nitrification rate due to bacterial growth rate change in fixed film processes is greatly reduced compared with that of suspended growth processes. When oxygen is limited, the decrease in saturation DO concentration as temperature increases results in a negative temperature impact upon the nitrification rate.  相似文献   
4.
Nitrification kinetics of biofilm as affected by water quality factors   总被引:12,自引:0,他引:12  
Various types of fixed film biofilters have been used in recirculating aquaculture systems under different water quality and operating conditions. The effectiveness of the nitrification process can be evaluated by nitrification kinetics. Nitrification in the bacterial film of the biofilter involves physical, chemical and biological processes that are governed by a variety of parameters such as substrate and dissolved oxygen concentrations, organic matters, temperature, pH, alkalinity, salinity and turbulence level. The impacts of these parameters upon nitrification kinetics make predicting the performance of a biofilter for a given application an engineering challenge. Knowing the performance of a biofilter is critical for both designers and managers. This paper summarizes the current knowledge on nitrification kinetics as affected by the aforementioned factors based on literature and the results from the authors’ laboratories. These factors were ranked according to their significance of impact on biofilter nitrification performance. The information presented can be used as a reference for the design and operation of biofilters in recirculating aquaculture systems.  相似文献   
5.
This paper presents the first laboratory study investigating larval settlement and metamorphosis of Pinctada maxima in response to both natural and artificial inducers. Natural biofilms induced larval settlement and the inductive effect appears to be closely associated with the bacteria in the biofilm. This result indicates that, in nature, bacteria may play an important role in the settlement of P. maxima larvae. Various pharmacological agents were also tested in this study and the results were generally similar to those found with other marine invertebrates, particularly molluscs. The results show that some pharmacological agents are potent artificial inducers of larval settlement for P. maxima. The findings of this study provide valuable information for understanding the mechanism of the larval settlement of this species, which is useful information for the hatchery industry of this pearl oyster.  相似文献   
6.
7.
[目的]明确五倍子(Rhus chinenis)、石榴皮(Folium sennae)对溶藻弧菌(Vibrio alginolyticus)及其生物膜的体外抑制作用。[方法]采用琼脂扩散法,分别测定五倍子、石榴皮对溶藻弧菌的体外抑菌作用;选用倍比稀释法确定五倍子、石榴皮对溶藻弧菌的最小抑菌浓度(MIC)和最小杀菌浓度(MBC);采用改良微孔板法评价2种中草药液对溶藻弧菌生物膜形成的影响。[结果]2种中草药都有不同程度的抑制溶藻弧菌的作用,五倍子对溶藻弧菌的抑菌圈直径为(16.37±0.14)mm,MIC和MBC均为6.25 mg/m L;石榴皮对溶藻弧菌的抑菌圈直径为(12.37±0.06)mm,MIC和MBC分别为12.50、25.00 mg/m L。当药物浓度在1.56 mg/m L及以上时,五倍子对溶藻弧菌生物膜的形成有极显著抑制作用;药物浓度在6.25 mg/m L及以上时,石榴皮对溶藻弧菌生物膜的形成有极显著抑制作用。[结论]五倍子和石榴皮对溶藻弧菌及其生物膜均有抑制作用。  相似文献   
8.
[目的]为灰水的利用提供依据。[方法]利用改进型微动力一体式生物膜反应器处理灰水,监测了进出水的CODCr、LAS、TN和SS以及反应器的温度、pH值和DO。[结果]进水CODCr平均为188 mg/L,出水CODCr平均为32 mg/L,CODCr去除率为80.2%~86.9%。当水力停留时间(HRT)≤3 h时,系统对污染物的去除率随停留时间的延长增长较快。当HRT>3 h时,系统对污染物的去除率随停留时间的延长增长变缓;HRT=3.5 h时,系统对CODCr、LAS的去除率分别为91.7%、81.2%。反应器在常温下按HRT=3.5 h运行时,处理后灰水符合《生活杂用水水质标准》的要求。CODCr、LAS的去除率随温度变化变化不大,TN的去除率下降了40.4%。[结论]改进型微动力一体化生物膜反应器的最佳水力停留时间为3.5 h,系统对CODCr、LAS的去除率分别为91.7%、81.2%。  相似文献   
9.
李国朝  张新华  陈捷  杨涛 《安徽农业科学》2011,(10):5994-5995,6003
通过小试试验,研究了以玉米芯为反硝化碳源和生物膜载体的生物反应器在启动阶段对污水中COD及硝酸盐的去除效果。结果表明,在模拟废水COD100 mg/L、NO3--N40 mg/L,pH值6.5~7.5条件下,13 d挂膜后间歇处理后的废水COD可降至30 mg/L,18 d挂膜后废水NO3--N降至2 mg/L以下。  相似文献   
10.
不同环境因素对表皮葡萄球菌生物膜形成的影响   总被引:1,自引:0,他引:1  
采用微量板半定量法研究影响表皮葡萄球菌生物膜形成的因素,同时模拟奶牛体内环境因素,如乳糖、酪蛋白和Ca2+等,探索不同理化因素对表皮葡萄球菌生物膜形成的影响,结果表明,检测的3种培养基中,胰蛋白胨大豆肉汤(Typtic Soy Broth,TSB)培养基最有利于表皮葡萄球菌的生长及其生物膜的形成,且最适质量分数为3%左右;在pH中性条件下,NaCl对表皮葡萄球菌生物膜的形成有明显抑制作用;当pH大于7时,表皮葡萄球菌生物膜形成能力明显减弱。在模拟奶牛体内环境因素中,一定质量分数的Ca2+(0.2%及以上)与高质量分数的乳糖(8%及以上)对生物膜形成有明显抑制作用,而外源添加酪蛋白对表皮葡萄球菌生物膜形成没有明显影响。  相似文献   
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