Effect of bovine manure on Cryptosporidium parvum oocyst attachment to soil

The objective of this work was to assess the effect of dilute bovine manure (1.0% and 0.1%) versus that of no manure on attachment and subsequent detachment of Cryptosporidium parvum oocysts to soil. Manure enhanced the attachment of oocysts to soil particles; the maximum attachment was observed with 0.1% manure. Oocyst attachment was partially reversible; maximum detachment was observed with dilute manure. These results indicate that oocyst attachment to soil is substantially affected by bovine manure in a complex manner and should have implications for how oocysts may be transported through or over soils.     

不同粒径红壤胶体颗粒对DNA的吸附特性

采用平衡法研究了含有机质粗粘粒、去有机质粗粘粒、含有机质细粘粒和去有机质细粘粒4种红壤胶粒对DNA的吸附特征及其热力学特性.结果表明: 4种红壤胶粒对DNA的吸附是快反应过程,Langmuir吸附方程可较好地描述4种红壤胶体对DNA的等温吸附,相应拟合的相关系数r²分别为0.974、0.991、0.958和0.975.最大吸附量表现为含有机质细粘粒>去有机质细粘粒>含有机质粗粘粒>去有机质粗粘粒.电解质浓度和种类及吸附体系pH是影响红壤胶体对DNA吸附的重要因子,一定电解质浓度范围(NaCl<60 mmol·L^-1,CaCl₂<10 mmol·L^-1)内,DNA在红壤胶体表面的吸附量随电解质浓度的增大而显著增加,其中钙离子的促进作用大于钠离子,但随着吸附体系pH的上升而显著降低.含有机质胶粒对DNA的吸附过程是吸热反应,而去有机质胶粒对DNA的吸附过程是放热反应,红壤胶粒对DNA的吸附反应过程是一个熵增过程.     

Comparison of fecal coliform agar and violet red bile lactose agar for fecal coliform enumeration in foods

A 24-h direct plating method for fecal coliform enumeration with a resuscitation step (preincubation for 2 h at 37 +/- 1 degrees C and transfer to 44 +/- 1 degrees C for 22 h) using fecal coliform agar (FCA) was compared with the 24-h standardized violet red bile lactose agar (VRBL) method. FCA and VRBL have equivalent specificities and sensitivities, except for lactose-positive non-fecal coliforms such as Hafnia alvei, which could form typical colonies on FCA and VRBL. Recovery of cold-stressed Escherichia coli in mashed potatoes on FCA was about 1 log unit lower than that with VRBL. When the FCA method was compared with standard VRBL for enumeration of fecal coliforms, based on counting carried out on 170 different food samples, results were not significantly different (P > 0.05). Based on 203 typical identified colonies selected as found on VRBL and FCA, the latter medium appears to allow the enumeration of more true fecal coliforms and has higher performance in certain ways (specificity, sensitivity, and negative and positive predictive values) than VRBL. Most colonies clearly identified on both media were E. coli and H. alvei, a non-fecal coliform. Therefore, the replacement of fecal coliform enumeration by E. coli enumeration to estimate food sanitary quality should be recommended.     

Phosphorus and carbohydrate limitation of fecal coliform and fecal enterococcus within tidal creek sediments

Aquatic sediments can be a significant reservoir of bacterial indicators of fecal contamination at levels higher than the waters above them. Several environmental factors have been identified that can enhance the role of sediments as a reservoir for enteric pathogens, including carbon and/or phosphorus availability. In order to investigate the influence of these and other environmental factors on sediment fecal bacteria populations, sediment samples were collected from a coastal watershed in southeastern North Carolina and analyzed for fecal coliform and fecal enterococcus using a modified membrane filtration technique. Measurements of sediment phosphorus, sediment carbohydrate, and environmental factors were made and relationships with bacteria concentrations were assessed. These observations were accompanied by an experimental laboratory manipulation of phosphorus and carbohydrate and their effects on sediment-associated fecal coliform and enterococcus. Field results suggested that sediment-associated indicator bacteria were not limited by sediment phosphorus or carbohydrate. Experimental results suggested that sediment-associated fecal bacteria were more frequently limited by bioavailable carbohydrate. Sediment phosphorus was limiting for fecal enterococcus only where sediment P was initially low (<31 μg P g⁻¹). A strong positive response by sediment fecal coliform concentrations to recent (24 h) precipitation was evidence that stormwater runoff delivers fecal bacteria loadings that are only partly measurable by conventional water sampling schemes, and by driving sediment and sediment P-loading plays a significant role in enhancing aquatic sediments as reservoirs for fecal microbes.     

Survival of faecal indicator bacteria in bovine manure incorporated into soil

AIMS: Survival of Escherichia coli and enterococci was evaluated in bovine manure incorporated into two Wisconsin soils. METHODS AND RESULTS: Silty clay loam (SCL) and loamy sand (LS) were mixed with fresh bovine manure, exposed daily to 10 h at 22 degrees C/14 h at 9 degrees C, and watered weekly for 12 weeks. Escherichia coli numbers increased 1-2 log cfu g(-1), then decreased < 1 and about 2 log cfu g(-1) in SCL and LS, respectively. Enterococci numbers rose less and then declined faster than those of E. coli. Watering intervals of 3, 7 and 14 days were evaluated in weeks 13-19, but did not affect the slow decline in numbers of E. coli or enterococci. CONCLUSION: Escherichia coli and enterococci may survive at least 19 weeks at 9-21 degrees C in bovine manure/soil, with E. coli surviving better. SIGNIFICANCE AND IMPACT OF THE STUDY: Quantification of E. coli or enterococci in late spring/early summer soil may be useful in indicating recent application of bovine manure.     

Effect of dredge spoil deposition on fecal coliform counts in sediments at a disposal site.

The most-probable-number of fecal coliforms in sediments was monitored at the New London dump site in Long Island Sound during the deposition of dredge spoil from the Thames River. Although the geometric mean for fecal coliforms at five stations in the river was 14,000/100 ml before dredging commenced, the deposition of this material did not increase the incidence of fecal coliforms at 17 spoil stations and 13 control stations in the disposal and surrounding areas. Fecal coliforms appear to occur only in the surface sediment material and are diluted by the subsurface material during the dredging operation. Fecal coliform analyses of bottom waters during high and low tides indicated that the flow of water from the Thames River played a major role in determining the most-probable-number of fecal coliforms in the sediments at the disposal site.     

Effect of dredge spoil deposition on fecal coliform counts in sediments at a disposal site.

The most-probable-number of fecal coliforms in sediments was monitored at the New London dump site in Long Island Sound during the deposition of dredge spoil from the Thames River. Although the geometric mean for fecal coliforms at five stations in the river was 14,000/100 ml before dredging commenced, the deposition of this material did not increase the incidence of fecal coliforms at 17 spoil stations and 13 control stations in the disposal and surrounding areas. Fecal coliforms appear to occur only in the surface sediment material and are diluted by the subsurface material during the dredging operation. Fecal coliform analyses of bottom waters during high and low tides indicated that the flow of water from the Thames River played a major role in determining the most-probable-number of fecal coliforms in the sediments at the disposal site.     

Soil microbial community responses to antibiotic-contaminated manure under different soil moisture regimes

Sulfadiazine (SDZ) is an antibiotic frequently administered to livestock, and it alters microbial communities when entering soils with animal manure, but understanding the interactions of these effects to the prevailing climatic regime has eluded researchers. A climatic factor that strongly controls microbial activity is soil moisture. Here, we hypothesized that the effects of SDZ on soil microbial communities will be modulated depending on the soil moisture conditions. To test this hypothesis, we performed a 49-day fully controlled climate chamber pot experiments with soil grown with Dactylis glomerata (L.). Manure-amended pots without or with SDZ contamination were incubated under a dynamic moisture regime (DMR) with repeated drying and rewetting changes of >20 % maximum water holding capacity (WHC_max) in comparison to a control moisture regime (CMR) at an average soil moisture of 38 % WHC_max. We then monitored changes in SDZ concentration as well as in the phenotypic phospholipid fatty acid and genotypic 16S rRNA gene fragment patterns of the microbial community after 7, 20, 27, 34, and 49 days of incubation. The results showed that strongly changing water supply made SDZ accessible to mild extraction in the short term. As a result, and despite rather small SDZ effects on community structures, the PLFA-derived microbial biomass was suppressed in the SDZ-contaminated DMR soils relative to the CMR ones, indicating that dynamic moisture changes accelerate the susceptibility of the soil microbial community to antibiotics.     

Distribution of blood-borne particles of two different sizes in rat spleens

Polystyrene microspheres 5 micron in diameter and Indian ink, consisting of particles 0.03 micron in diameter, were injected into the splenic artery in rats. The distribution of the polystyrene microspheres and the ink particles in the spleen were examined microscopically and morphometrically. The polystyrene microspheres appeared mainly in the red pulp, and the Indian ink particles mostly in the marginal zone, which functions as an immunological filter. (No arteries opened into the lymphoid follicles.)     

发酵肥与秸杆还田对土壤微生物区系与作物产量的影响

土壤中施入不发酵新鲜粪肥时土壤细菌与放线菌数量明显增加,当施入发酵肥时对土壤微生物活性影响较小;在施发酵肥基础上再进行秸杆还田,土壤微生物活性明显提高,作物获得持续丰产。单一秸杆还田也能提高土壤微生物活性,但当年无增产效果,在秸杆还田时喷雾接种木霉（Ｔｒｉｃｈｏｄｅｍａｋｏｎｉｎｇｉ）４５６—２与固氮菌（Ａｚ．ｖｉｎｅｌａｎｄｉｉ）２３０,当年获得增产效果。     

Effects of the core lipid on the energetics of binding of ApoA-I to model lipoprotein particles of different sizes

Interaction of apolipoproteins (apo) with lipid surfaces plays crucial roles in lipoprotein metabolism and cholesterol homeostasis. To elucidate the thermodynamics of binding of apoA-I to lipid, we used lipid emulsions composed of triolein (TO) and egg phosphatidylcholine (PC) as lipoprotein models. Determination of the level of binding of wild-type (WT) apoA-I and some deletion mutants to large (120 nm diameter; LEM) and small (35 nm diameter; SEM) emulsions indicated that N-terminal (residues 44-65) and C-terminal (residues 190-243 and 223-243) deletions have large effects on lipid interaction, whereas deletion of the central region (residues 123-166) has little effect. Substitution of amino acids at either L230 or L230, L233, and Y236 with proline residues also decreases the level of binding, indicating that an alpha-helix conformation in this C-terminal region is required for efficient lipid binding. Calorimetry showed that binding of WT apoA-I to SEM generates endothermic heat (DeltaH approximately 30 kcal/mol) in contrast to the exothermic heat (ca. -85 kcal/mol) generated upon binding to LEM and egg PC small unilamellar vesicles (SUV). This exothermic heat arises from an approximately 25% increase in alpha-helix content, and it drives the binding of apoA-I to LEM and SUV. There is a similar increase in alpha-helix content of apoA-I upon binding to either SEM or SUV, but the binding of apoA-I to SEM is an entropy-driven process. These results suggest that the presence of a core triglyceride modifies the highly curved SEM surface packing and thereby the thermodynamics of apoA-I binding in a manner that compensates for the exothermic heat generated by alpha-helix formation.     

施用牛粪和绿肥对土地整治区玉米产量和土壤理化性质的影响

采用定位试验,研究了施用新鲜牛粪(15000和75000 kg·hm^-2)和绿肥(36000 kg·hm^-2)对玉米产量、土壤呼吸和土壤化学、物理性状的影响.结果表明: 与单施化肥相比,土地整治区施用牛粪的玉米籽粒增产7.2%～29.9%,千粒重增加2.5%～18.2%,活性有机碳和有机质含量分别增加5.3%～34.6%和8.0%～17.6%.施用绿肥的玉米籽粒增产10.8%～15.6%,千粒重增加4.5%～8.4%,活性有机碳含量增加14.1%～48.6%,在第二年土壤有机质含量增加了7.2%.施用牛粪和绿肥的土壤呼吸速率增加了20.0%～69.3%.施用牛粪和绿肥增加了土壤容重,减少了总孔隙度和毛管孔隙度,分别增加了＜0.01 mm和0.05～1 mm粒径团聚体的比例.连续2年在土地整治区施用牛粪和绿肥不仅能够增加玉米籽粒产量,而且已经对土壤物理化学性质的改善表现出积极的作用.     

轮作及绿肥不同利用方式对作物产量和土壤肥力的影响

通过4年田间定位试验比较了3种轮作及相应绿肥不同利用方式对作物产量和土壤性质的影响.轮作方式包括夏休闲-冬小麦（对照）、豆类绿肥-冬小麦和豆类绿肥-春玉米-冬小麦.豆类绿肥-冬小麦包括3种绿肥利用方式：提前覆盖、提前翻压和播前翻压;豆类绿肥-春玉米-冬小麦也包括3种绿肥利用方式：豆类茎秆覆盖、茎秆翻压和茎秆移出田间.结果表明：对于豆类绿肥-冬小麦轮作,绿肥消耗了更多小麦播前土壤水,使小麦产量不稳定;麦收后0～200 cm土层硝态氮储量显著高于另外两种轮作,有更高的淋失风险;该轮作方式下提前覆盖处理0～20 cm土层土壤有机碳(SOC)含量和有机碳储量(SSOC)最高.对于豆类绿肥-春玉米-冬小麦轮作,小麦播前土壤储水量显著高于豆类绿肥-冬小麦,小麦产量更稳定;麦收后0～200 cm土层硝态氮储量显著低于豆类绿肥-冬小麦轮作,淋失风险较低;该轮作方式下茎杆覆盖处理0～20 cm土层土壤SOC含量显著高于茎杆移出处理,且SSOC相对于试验初始也有所增加.可见,豆类绿肥-春玉米-冬小麦轮作体系中豆类收获籽粒后茎杆地表覆盖方式,在提高小麦播前土壤储水量、稳定产量、培肥土壤和降低0～200 cm土层土壤硝态氮残留量上表现较好,是具有类似气候地区的合理种植制度.
     

Incidence of R factors in coliform, fecal coliform, and Salmonella populations of the Red River in Canada.

Coliforms, fecal coliforms, and Salmonella were isolated from the Red River, Manitoba, Canada, and identified. These organisms were then examined for resistance to 12 antibiotics. Some fecal coliforms were resistant to all 12 antibiotics, and 18% of the Salmonella isolates were resistant to one or more antibiotics. A total of 52.9% of the fecal coliforms resistant to three or more antibiotics were able to transfer single or multiple resistance (R) determinants to the Salmonella recipient, and 40.7% could transfer R determinants to the Escherichia coli recipient. Of the resistant Salmonella, 57% transferred one or two determinants to the Salmonella recipient, and 39% transferred one or two determinants to the E. coli recipient. It was calculated that populations of fecal coliforms containing R factors were as high as 1,400 per 100 ml and that an accidental intake of a few milliliters of water could lead to transient or permanent colonization of the digestive tract. Consideration of data on bacteria with R factors should be made in future water quality deliberations and in discharge regulations.     

猪粪和稻草对镉污染黄泥土生物活性的影响

通过培养试验研究了猪粪和稻草对Cd污染黄泥土生物活性的影响,结果表明,Cd污染土壤的生物活性下降,施用有机肥料后,土壤有效态Cd含量降低,降幅约为40％;微生物量C、N、P和脱氢酶、过氧化氢酶的活性增高,增幅为30％～100％,其中微生物量C、N与土壤有效态Cd之间有显著的负相关关系,可作为污染土壤的生物指标。     

Microbial attachment to particles in marine and freshwater ecosystems

Scanning electron microscopy observations ofin situ suspended marine and freshwater particles show diverse but similar modes of bacterial and fungal attachment. A survey of Sierra Nevada mountain lakes and pelagic and near-shore waters in the Pacific Ocean indicates that attachment is most noticeable in the near-surface waters where fresh dissolved and particulate input of carbon from phytoplankton and elevated temperatures favor microbial growth. The most common modes of attachment are: adhesive stalk formation, growth on adhesive webs, attachment by the use of pili-like appendages and slimy capsular secretions, and molecular or chemical sorption without the use of visualized structural appendages. Attached microbial growth is accelerated when particulate substrates are supplied, even when they are not rich in organic nutrients. This is the case in the Lake Tahoe basin, where microflora attached to eroded silts can significantly modify the organic carbon and nutrient content of such minerogenous particles.     

Effects of different organic waste amendments on soil microaggregates stability and molecular sizes of humic substances

Three soils which had been amended for several years with pig slurry, cattle slurry, and sewage sludge were dry-sieved to obtain microaggregates in the size range of 250–125, 125–50, and <50 μm. With amendments, aggregate size distribution of whole soils was shifted to larger sizes, especially for the most fragile soil, whereas percent content of microaggregates decreased except for the lower size aggregates of the fragile soil. Particle size distribution of microaggregates revealed an increase in percent sand and a reduction of percent silt and clay in the <50 μg size fraction for all soils. These results showed the aggregation effect induced by the organic waste additions. Aggregate stability of microaggregates revealed significant correlation with humic substances content (humic acids alone and humic plus fulvic acids) and non significant with total organic matter substantiating the belief that humic substances are the predominant binding agents in this aggregation range. Molecular weight distribution of humic acids extracted from microaggregates of unamended soils demonstrated that the lower the soil aggregate size distribution, the larger the contribution of the high molecular weight fraction. All microaggregates from amended soils showed a progressive increase of the high molecular weight humic acids with decreasing size, reaching a maximum in the <50 μm fraction. In this aggregate size a parallel enhancement of the aggregate stability was also evident. It is concluded that a close relationship exists between aggregate stability and high molecular weight humic substances. Additions to soils of organic material containing high molecular weight constituents would represent a useful management practice to improve aggregate stability.     

施用有机肥对棕壤和草甸土固钾作用的影响研究

通过室内恒湿和干湿交替培养试验,研究了沈阳地区耕地棕壤和草甸土的固钾特征,及其施用有机肥后对土壤固钾作用的影响。结果表明,在保持土壤处于田间持水量的恒湿条件下,两种土壤对外源钾都能够产生快速固定作用,经过1d培养土壤的固钾作用就可以达到平衡,但干湿交替培养可以提高土壤固钾量26．80％～33．27％;土壤施用有机肥后,在恒湿和干湿交替培养条件下均可以降低土壤的固钾强度,其中,施用有机肥6％处理的恒湿培养15d后,棕壤和草甸土的固钾量分别降低了25．71％和36．62％。