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S. Cakmakci E. Dagdemir A. A. Hayaloglu M. Gurses E. Gundogdu 《World journal of microbiology & biotechnology》2008,24(3):293-299
The objective of the present study was to investigate the influence of container material (plastic or goat-skin bag) on the
growth of lactic acid bacteria in Tulum cheese during 9 months of ripening. The lactic acid bacteria in Tulum cheeses were
periodically counted on MRS and M17 agars throughout ripening. Results showed that the highest counts of lactic acid bacteria
on MRS or M17 were observed at the beginning of ripening and their counts decreased during later stages of ripening. The cheese
samples ripened in plastic bags exhibited higher numbers of LAB on MRS and M-17 agars than those ripened in goat-skin bags.
A total of 112 strains of lactic acid bacteria were isolated from Tulum cheeses ripened in plastic or goat-skin bags during
ripening. The lactic acid bacteria present in the cheese were classified by Microbial Identification System (MIS) based on
a comparison of the fatty acid methyl ester profiles. Different species including Enteroccocus, Lactobacillus, Streptococcus, Lactococcus and Pediococcus genera were found in unripened cheese. As ripening proceeded, the species Streptococcus and Lactococcus disappeared and the percentages of the species Enterococcus was unchanged in both containers. There were slight differences between the cheeses ripened in plastic or goat-skin bags
in terms of the profiles of lactic acid bacteria isolated. Some species including L. brevis, L. mesenteroides subsp. dextranicum, P. damnosus and E. mundtii were isolated only in the cheeses ripened in plastic bags; however, L. coryniformis and L. malafermentans were isolated only in the cheeses ripened in goat-skin bags at 6 or 9 months of ripening. Also the numbers of E. faecalis isolates were higher in the cheeses ripened in plastic containers than cheeses ripened goat-skin bags at the 6 or 9 months
of ripening. The results showed that Lactobacillus and Enterococcus were the predominant species in matured Tulum cheeses in both ripening containers. It seemed possible to produce Tulum cheese
with similar characteristics from both the containers used. 相似文献
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The role of lactic acid bacteria in accelerated cheese ripening 总被引:4,自引:0,他引:4
Morsi A. El Soda 《FEMS microbiology reviews》1993,12(1-3):239-251
Abstract: The ripening of cheese is a slow and consequently an expensive process. The economic advantage of rapid development of more intense cheese flavour in shorter periods of time would be substantial. Lactic acid bacteria play a key role during ripening and can therefore be used as accelerating agents. This review describes the different strategies where lactic acid bacteria or their enzymes were used to reduce the ripening time of cheese. The advantages, limitations and technical feasibility as well as the commercial potential of the different approaches are also considered. 相似文献
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The spatial and temporal distribution of nematodes in two low rate percolating filter bed sewage treatment plants at Carnforth
and Caton, Lancashire, were investigated. Nematodes were abundant reaching densities up to 900 cm−2 of media surface. Numbers decreased down the bed and species composition displayed spatial differences with bed depth. Eight
orders of nematode were represented, members of the sub-family Diplogasterinae and Rhabditinae were particularly common. A
seasonal pattern of abundance was clearly apparent; two peaks occurred, one in May and a second during the winter months.
Lowest numbers corresponded with periods of highest temperature. The demise of the nematodes in the spring was related to
the sloughing of the surface film on the media. 相似文献
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Seasonal and spatial distribution pattern of nitrogen fixing bacteria in fish ponds under different management systems 总被引:1,自引:0,他引:1
Enumeration of nitrogen fixing bacterial population in water and sediment samples of six fish farming ponds (polyculture, monoculture and traditional systems) over a period of two and a half years revealed significant differences between the culture systems with maximal and lowest counts in the monoculture and traditional systems, respectively. Polynomial equations of the 2nd to 4th degree were used to represent the observed seasonal data in these ponds. The bacterial populations peaked in summer, while the lowest count was observed in winter. The environmental factors such as pH, different species of nitrogen, dissolved organic carbon were responsible for the seasonal changes in nitrogen fixing bacteria. 相似文献
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青杨脊虎天牛幼虫空间分布格局 总被引:9,自引:0,他引:9
20 0 3年 4~ 6月 ,在黑龙江省大庆市红旗林场对青杨脊虎天牛XylotechusrusticusL .幼虫空间分布格局进行了调查研究 ,结果表明该天牛幼虫在杨树人工林内呈负二项分布 ;采用 6种不同聚集指标测定结果均表明为聚集分布。对青杨脊虎天牛幼虫在树干高度上垂直分布研究表明 ,该天牛幼虫在树干上危害部位主要集中在 1~ 4m范围内 ;对该幼虫垂直分布与树干高度进行曲线拟合 ,符合立方曲线 ,曲线方程为y =0 0 68+0 41 7x -0 1 3 6x2 +0 0 1 1x3 ,由相关系数方值R2 =0 83 6验证 相似文献
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Quadrat analysis was used to investigate the spatial distribution of seven mammalian cell lines in culture. The number of
cells in replicate unit areas of the culture was determined, and the variance to mean ratio used as an index of random and
nonrandom spatial distribution. Only mouse SV3T3 cells distributed themselves randomly throughout the entire culture growth
cycle. The remaining six lines all assumed a nonrandom distribution at some point in their growth cycles. Mouse L929 cells
displayed avoidance behavior, and spaced themselves at regular intervals in a uniform spatial distribution. The five remaining
lines (mouse S180, rat C6, hamster CHO, canine MDCK, and human BeWo) formed multicellular clusters, and were distributed aggregatively
rather than randomly. Random walk migration can account for the random distribution of SV3T3 cells. Random walk combined with
contact inhibition of movement provides a satisfactory explanation for the uniform distribution of L929 cells. Random walk
and contact inhibition are incompatible with cell clustering, however. Thus other mechanisms of motility or adhesiveness must
contribute to cell clustering. It is possible that random walk and contact inhibition may be less common components of cell
movement than generally assumed. 相似文献
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John Conlisk Erin Conlisk Abd. Rahman Kassim Ian Billick John Harte 《Global Ecology and Biogeography》2012,21(12):1167-1178
Aim The shape of a species' spatial abundance distribution may change with spatial scale. We predict that the shape will typically change from strictly downward‐sloping (falling) to humped (rising then falling) as the spatial scale increases. The prediction, motivated in part by central limit reasoning, is intended for common or abundant species over reasonably homogeneous habitats. We test the prediction using data on 800+ tree species, one ant species, and 14 bird species. Location Tree data are for Malaysia and Central America; ant and bird data are for North America. Methods For each species, histograms and relative mode shape statistics are compared across multiple spatial scales. Results The predicted pattern is broadly confirmed. Main conclusions The emerging hump pattern is a candidate for listing among macroecological regularities. In appropriate contexts, spatial theories might be asked to predict the pattern. 相似文献
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长江口浮游甲壳动物空间分布特征 总被引:1,自引:0,他引:1
2010年研究了长江口南、北支浮游甲壳动物的空间分布特征。共采集到浮游甲壳动物50种,其中桡足类39种,枝角类11种。种类数南支高于北支;平均密度北支高于南支,南、北支分别为1.7 ind./L和61.8 ind./L。基于群落相似性矩阵的CLUSTER聚类和MDS分析显示,在群落相似性为40%时,长江口区域浮游甲壳动物群落可分为北支组、南支组1和南支组2共3组。3组的优势种有差异。浮游甲壳动物的平均密度变化趋势为北支组(61.8±22.11 ind./L)〉南支组1(3.07±2.06 ind./L)〉南支组2(0.72±0.45 ind./L)。盐度、潮汐和径流量是影响长江口南北支浮游甲壳动物种类组成、密度和空间分布差异的重要环境因素。 相似文献
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玉米根系形态性状和空间分布对水分利用效率的调控 总被引:23,自引:0,他引:23
玉米根系形态性状(总根长、根系表面积和根系干物质重)与植物整体水分利用效率间具有显著或极显著的相关性,回归曲线趋势基本相同,均呈二次曲线关系,只是相关系数不同。说明从提高水分利用效率来说,根系需要维持适宜的大小。其中根长对水分利用效率的贡献是第一位的,而根系干物质重的贡献最小,根系表面积介于二者之间。从空间分布来说,玉米每层节根数、节根长度和直径在父母本和杂交种间也具有显著或极显著的差异。与中下层根量相比,母本与不抗旱的父本处于上层干土中的根系数量明显较多,且根系直径大,吸水困难。而杂交种在干旱条件下上层根重和数量维持不变,或略高于不抗旱品种,但中层和下层根系数量和长度明显高于不抗旱品种,且根系直径小于不抗旱品种,这样从多的有效根系数量和低的吸水阻力两方面保证了水分的吸收,从而使其产量和水分利用效率均最高,说明通过根系形态特性和空间分布的优化能够调节作物整体的水分利用效率。 相似文献
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为准确掌握苹果蠹蛾Cydia pomonella(L.)的田间发生动态,本文对苹果园中苹果蠹蛾卵的空间分布格局和抽样技术进行了研究。结果表明:在第2代卵发生高峰期,苹果叶片上的苹果蠹蛾卵量显著高于果实上的卵量(叶片上着卵量占总卵量的58.2%,P<0.05),叶片上的卵主要分布于叶片正面(正面着卵量占叶片上总卵量的69.6%,P<0.05);在树冠不同方位上,东、南两面的着卵量最大,但在不同空间层次上分布的卵量没有差异。卵在叶片和果实上均呈聚集分布,且聚集强度随种群密度的升高而增加,其聚集是由环境因素造成的。文中还根据Taylor幂法则参数建立了苹果蠹蛾卵的理论抽样数模型。 相似文献
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西藏草地生态系统植被碳贮量及其空间分布格局 总被引:4,自引:0,他引:4
在广泛收集资料的基础上,利用平均碳密度方法,估算了西藏高原草地生态系统17类草地植被的碳贮量,并分析了其空间分布格局.结果表明:(1)17类草地植被总面积为8205.194×104hm2,总碳贮量为189.367 Tg (1TgC=1012g),平均碳密度为2307.895 kgC/hm2,不同植被类型差异较大,在395.977~20471.161kgC/hm2之间波动;(2)从草地类型分布看,高寒草原和高寒草甸是西藏分布面积最大的2类草地,分布面积占西藏草地总面积的70.210%,又是西藏草地碳贮量的主要贮库,碳贮量占西藏草地总碳贮量的79.393%;(3)在空间分布格局上,随着自藏东南向西北的延伸,草地植被总碳密度逐次降低,这一水平分布格局与西藏独特的水热分布相一致;碳密度的垂直分布规律因地区而异,但各地区均以高寒草甸或高寒荒漠的低碳密度为终点,表现出"殊途同归"的特征. 相似文献
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青藏高原那曲地区冬虫夏草资源分布空间分析方法 总被引:5,自引:2,他引:5
冬虫夏草(Cordyceps sinensis)是分布在我国青藏高原的可再生资源,具有极其名贵的中药材价值,而目前我国冬虫夏草资源的分布区域尚不清楚。以西藏那曲地区为例,根据冬虫夏草资源分布的生境条件,结合冬虫夏草的生态特性指标,利用地理信息系统(GIS)空间分析方法对冬虫夏草的空间分布区域进行了分析。结果表明,那曲地区冬虫夏草资源主要分布于那曲的东部,分布面积约为4.93万km2,占地区总面积的12.54%。与实地调查结果比较,提出的基于GIS空间分析的冬虫夏草分布区分析方法精度较高,说明空间分析方法在冬虫夏草资源调查评价上具有一定的可行性,为今后的冬虫夏草资源调查等相关研究提供方法支持。 相似文献