A synthesis of the effects of pesticides on microbial persistence in aquatic ecosystems

Pesticides have a pervasive presence in aquatic ecosystems throughout the world. While pesticides are intended to control fungi, insects, and other pests, their mechanisms of action are often not specific enough to prevent unintended effects, such as on non-target microbial populations. Microorganisms, including algae and cyanobacteria, protozoa, aquatic fungi, and bacteria, form the basis of many food webs and are responsible for crucial aspects of biogeochemical cycling; therefore, the potential for pesticides to alter microbial community structures must be understood to preserve ecosystem services. This review examines studies that focused on direct population-level effects and indirect community-level effects of pesticides on microorganisms. Generally, insecticides, herbicides, and fungicides were found to have adverse direct effects on algal and fungal species. Insecticides and fungicides also had deleterious direct effects in the majority of studies examining protozoa species, although herbicides were found to have inconsistent direct effects on protozoans. Our synthesis revealed mixed or no direct effects on bacterial species among all pesticide categories, with results highly dependent on the target species, chemical, and concentration used in the study. Examination of community-level, indirect effects revealed that all pesticide categories had a tendency to reduce higher trophic levels, thereby diminishing top-down pressures and favoring lower trophic levels. Often, indirect effects exerted greater influence than direct effects. However, few studies have been conducted to specifically address community-level effects of pesticides on microorganisms, and further research is necessary to better understand and predict the net effects of pesticides on ecosystem health.     

Activity of antimicrobial peptide mimetics in the oral cavity: I. Activity against biofilms of Candida albicans

Naturally occurring antimicrobial peptides hold promise as therapeutic agents against oral pathogens such as Candida albicans but numerous difficulties have slowed their development. Synthetic, non-peptidic analogs that mimic the properties of these peptides have many advantages and exhibit potent, selective antimicrobial activity. Several series of mimetics (with molecular weight < 1000) were developed and screened against oral Candida strains as a proof-of-principle for their antifungal properties. One phenylalkyne and several arylamide compounds with reduced mammalian cytotoxicities were found to be active against C. albicans. These compounds demonstrated rapid fungicidal activity in liquid culture even in the presence of saliva, and demonstrated synergy with standard antifungal agents. When assayed against biofilms grown on denture acrylic, the compounds exhibited potent fungicidal activity as measured by metabolic and fluorescent viability assays. Repeated passages in sub-minimum inhibitory concentration levels did not lead to resistant Candida, in contrast to fluconazole. Our results demonstrate the proof-of principle for the use of these compounds as anti-Candida agents, and their further testing is warranted as novel anti-Candida therapies.     

Characterization of health effects of wood dust exposures

Exposure to wood dust is a common occurrence in all countries and may cause various diseases. These include extrinsic allergic alveolitis, organic dust toxic syndrome, occupational asthma, non-asthmatic chronic airflow obstruction, and simple chronic bronchitis (mucus hypersecretion). Of these conditions, the most common are simple chronic bronchitis and non-asthmatic chronic airflow obstruction. The level and pattern of occurrence of these conditions varies with the type of wood dust, climatic conditions, and the manner in which it is handled, particularly the use of fungicides. The prevalence and characteristics of the conditions associated with wood dust exposure are very similar to those due to grain dust exposure.     

消毒剂881成份分析和消毒效果观察

881消毒剂为新研制的卤素化学杀菌药物,经测定主要成份为二氯-碘异氰尿酸.杀菌试验证明,当其溶液中有效氯(碘)为50～100ppm,作用5～10分钟,可将细菌芽胞杀灭99.99%以上.     

金线莲茎腐病菌的生物学特性及5种杀菌剂对其抑制作用

采用十字交叉法和血球计数板法分别测定不同培养温度、pH和光照条件对金线莲茎腐病菌菌丝生长状况和产孢量的影响;用菌丝生长速率法测定5种杀菌剂对金线莲茎腐病菌的抑制作用,为金线莲茎腐病的防治提供参考。结果表明该病菌菌丝生长、产孢的最适温度都为28 ℃,最适生长的pH为6~7,且光暗交替可促进菌落的生长和产孢。在5种杀菌剂中,戊唑醇乳油的EC₅₀为10.02 mg·L^-1,为多菌灵的92.50倍;其次是腈菌唑和福星乳油,EC₅₀分别为91.23,96.68 mg·L^-1。戊唑醇乳油对金线莲茎腐病菌的抑制作用最强,防治效果较好。     

Assessment of the acute toxic effects of the fungicide Ridomil plus 72 on aquatic organisms and soil micro‐organisms

The acute toxic effects of Ridomil plus 72 (Ridomil), used as a fungicide in agriculture, were studied under laboratory conditions. These effects on freshwater cladoceran (Chydorus eurynotus) and freshwater fish (Oreochromis niloticus) were determined using standard bioassay procedures. The 4 h LC₅₀ for Chydorus eurynotus was 6.9 mg/L and the 96 h LC₅₀ for Oreochromis niloticus was 1.1 mg/L. The toxicity of Ridomil to a mixed population of soil micro‐organisms was measured using oxygen uptake and growth as measured by turbidity. At short‐term exposure (48 min), Ridomil was moderately toxic to the culture at 5000 mg/L and above, based on an activity quotient (AQ) of 0.50–0.70. For longer exposure periods (up to 6 h), Ridomil was slightly toxic to the culture at 200 to 500 mg/L. At 1000 mg/L, Ridomil was moderately toxic and at 3000 mg/L and above, Ridomil was extremely toxic to soil microorganisms. The toxicity of metalaxyl (one of the two active ingredients of Ridomil) to these micro‐organisms was measured using growth as measured by the turbidity change. The average toxic endpoint (16 h IC₅₀) was 1100 mg/L. The acute toxic values of Ridomil found in these studies were much below the expected environmental concentrations resulting from normal applications of the chemical on a cocoa tree as a fungicide. ©2000 John Wiley & Sons, Inc. Environ Toxicol 15: 65–70, 2000     

Establishment and validation of microsampling techniques in wild rodents for ecotoxicological research

Compounds and products in the biocide and plant protection sector can only be registered after formal risk assessment to ensure safety for users and the environment. In bird and mammal risk assessment, this is routinely done using generic focal species as models, which are of particular exposure risk. Such a species is the common vole (Microtus arvalis) due to its high food intake relative to the low body weight. For wild species, biological samples, data and hence realistic exposure estimations are particularly difficult to obtain. In recent years, advances have been made in the techniques related to serial microsampling of laboratory mice and rats that allow for a reduction in sampling volumes. Similar progress in wild species sampling is missing. This study presents a proof of concept to dose wild rodents with relevant compounds and to draw serial, low volume blood samples suitable for state‐of‐the art toxicokinetic analyses. For the first time, the jugular vein of common voles was used to administer compounds (two frequently used fungicidal components). This procedure and the following microsampling of blood (2 × 10 μl six times within 24 hours) from the lateral tail vein did not affect body weight and mortality of voles. Samples were sufficient to detect dissipation patterns of the compounds from blood in toxicokinetic analysis. These results suggest that microsampling can be well translated from laboratory mice to wild rodent species and help to obtain realistic exposure estimates in wild rodents for ecotoxicological studies as well as to promote the 3R concept in studies with wild rodent species.