小麦内生细菌及其对根茎部主要病原真菌的抑制作用

对小麦植株不同生育期、不同器官的内生细菌进行了分离和数量变化分析.结果表明,根、茎、叶及未成熟籽粒等器官中存在大量的内生细菌,鲜组织中平均约含内生细菌5.0×10⁵ CFU·g^-1,其中根系中内生细菌数量达7.8×10⁵ CFU·g^-1,而茎秆、叶片和未成熟籽粒中内生细菌数量分别为4.8×10⁵、3.2×10⁵和2.8×10⁵ CFU·g^-1.内生细菌数量在不同生育期也存在差异,幼苗期平均约为3.1×10⁵ CFU·g^-1、拔节期和灌浆期分别为5.7×10⁵和7.0×10⁵ CFU·g^-1.不同小麦田块之间存在明显差异,长武县一田块植物鲜组织中内生细菌的数量为6.1×10⁵ CFU·g^-1,而大荔县一田块约为3.9×10⁵ CFU·g^-1.试验结果发现,对小麦全蚀病菌具有拮抗作用的内生细菌有51株、对小麦纹枯病菌具有抑制作用的内生细菌有45株.用平板对峙法测定,有71株对两种病原真菌均有拮抗作用,对小麦全蚀病菌抑菌圈直径大于10 mm的有23株,其中来源于根系、茎秆、叶片和籽粒的分别为6株、7株、9株和1株;对小麦纹枯病菌抑菌圈超过10 mm的有20株,其中来源于根系、茎秆、叶片和籽粒的分别为7株、5株、7株和1株,说明从小麦叶片诱捕分离的内生细菌中,对小麦全蚀病菌和纹枯病菌抑菌作用较强的分离株比率最高,其次为茎秆,而根部和未成熟籽粒中比例明显较低.     

一种复合微生态制剂对养殖水体中生物因子的影响

[目的]研究海水养殖池塘中投放以芽孢杆菌和假单胞菌为主的一种自主研发的微生态制剂对池塘养殖生物、微生物菌相、浮游生物的影响,以期为建立微生物生态调控技术体系提供参考.[方法]实验期间,每隔15d于试验池塘中泼洒微生态制剂一次,每月末取样测量水体和底泥中异养菌和弧菌密度、浮游生物种类和密度,实验结束时测量养殖生物的生长率和成活率.[结果]该微生态制剂能够显著提高南美白对虾和三疣梭子蟹的存活率和生长速度,试验组南美白对虾的存活率和体重增长率较对照组分别提高了11.3％和1 400％,试验组三疣梭子蟹的存活率和体重增长率较对照组分别提高了1.2％和37.5％;微生态制剂能够显著提高海水池塘的异养菌总数,从而抑制致病性弧菌的数量,试验组池水和底泥的异养菌平均密度在整个养殖期较对照组提高了58.5％和51.3％,而试验组水体中致病菌——弧菌的数量在整个养殖期较对照组降低了39.7％;微生态制剂使绿藻门和硅藻门的藻类密度明显增加,对蓝藻和甲藻的生长有抑制作用.[结论]该微生态制剂能够有效地改善养殖池塘中生物群落结构,提高某些养殖品种的生长速度.     

三江平原典型湿地土壤剖面有机碳及全氮分布与积累特征

研究了三江平原2类典型湿地(毛果苔草沼泽和芦苇沼泽)沉积物剖面有机碳、全氮的分布特征与积累现状.结果表明,2类沼泽剖面有机碳分布均具有明显的储碳层和淀积层;上层的储碳层厚度约为60 cm,有机碳平均含量分别为96和184 g·kg^-1,全氮平均含量分别为7.4和17.6 g·kg^-1;下层的淀积层内有机碳和全氮含量低而稳定.2类沼泽剖面有机碳和全氮含量随剖面深度增加而下降, 有机碳、全氮与容重之间相关均极显著(P＜0.01).2类典型湿地有机碳密度在20～40 cm剖面内最大.储碳层内,有机碳储量分别为1.83×10⁴和1.73×10⁴ t·km^-2,全氮储量分别为1.45×10³和1.67×10³ t·km^-2;100 cm以内,有机碳储量分别为2.86×10⁴和262×10⁴ t·km^-2,全氮储量分别为2.18×10³和2.49×10³ t·km^-2.植被类型对湿地剖面有机碳、全氮含量及储量均具有不同程度的影响.     

1株副溶血性弧菌Bh-06的分离、鉴定及其药敏试验

从患病的南美白对虾分离出1株副溶血性弧菌Bh-06,通过革兰染色和Biolog全自动细菌鉴定仪鉴定,并对健康南美白对虾进行攻毒试验和对该菌株进行药物敏感试验。试验结果表明:Bh-06菌株为革兰阴性弧菌,通过细菌自动鉴定仪鉴定为副溶血性弧菌;该菌在培养第5小时进入对数早期,对数期一直延续到25小时;该菌在1.0×106cfu/mL浓度时可引起南美白对虾发病,而且浓度越高,病症越严重;该菌对氧哌嗪青霉素产生高度的敏感性。     

不同食细菌线虫取食密度下线虫对细菌数量、活性及土壤氮素矿化的影响

采用悉生培养微缩体系,探讨了不同食细菌线虫取食密度下线虫(Caenorhabditis elegans) 对细菌(Bacillus subtilis)数量和活性及土壤氮素矿化的影响.结果表明,线虫对细菌的取食,促进了细菌的增殖,并在不同线虫取食密度下对细菌的增殖促进作用总体表现为:接种20条·g^-1＞10条·g^-1＞40条线虫·g^-1处理.线虫在促进细菌增殖的同时,明显提高了土壤呼吸强度和土壤蔗糖酶、脲酶和磷酸酶的活性,但不同取食密度处理间差异不明显.线虫与细菌之间的相互作用显著提高了土壤铵态氮和矿质态氮含量,促进了土壤氮的矿化.不同取食密度处理间,线虫对土壤氮素矿化的促进作用与对细菌的增殖促进作用趋势一致.     

刺参对浅海筏式贝类养殖系统的修复潜力

浅海筏式养殖滤食性贝类产生大量的粪便和假粪（总称生物沉积物）,对海水养殖环境产生一系列影响;而沉积食性海参能够有效清除颗粒有机物,在海水养殖系统中扮演“清道夫”的生态角色.为评估刺参在浅海筏式贝类养殖系统中的生物修复潜力,本文在不同季节现场研究了贝 参混养模式下刺参对贝类生物沉积物的摄食及生长和排泄特征.结果表明: 刺参能够在新设计的养殖设施中与滤食性贝类混养,最大生长率达0.34%·d^-1; 并可通过摄食有效清除贝类生物沉积物, 摄食率为0.1746 g·g^-1·d^-1（夏季,21.2 ℃）、0.0989 g·g^-1·d^-1（秋季,19.2 ℃）和0.0050 g·g^-1·d^-1（冬季,7.7 ℃）;刺参主要通过排泄溶解形态的NH₄⁺N和PO₄^3- -P来促进沉积物中营养盐的再生,其排泄率也呈现明显的季节变化.基于现场试验数据,估算了刺参在桑沟湾的生物修复潜力, 刺参与贝类混养可摄食4.5～159.6 kg·hm^-2·d^-1生物沉积物、排泄1 382.5～3 678.1 mmol·hm^-2·d^-1NH₄⁺ -N及74.6～335.7 mmol·hm^-2·d^-1PO₄^3--P.表明刺参对浅海筏式贝类养殖系统具有较大的生物修复潜力,贝-参混养模式不仅能够取得较大的生态效益,而且能显著增加养殖生产的经济效益.     

长江三峡地区退化生态系统土壤微生物的初步研究*

通过对长江三峡地区4种退化生态系统类型,每一类型5个土壤样品中微生物的初步研究, 结果表明该地区土壤每克干土中真菌和细菌的数量分别为 8.62×10⁴ ～1.31×10⁵ cfu 及 1.547×10⁷～6.957×10⁷ cfu, 但不同退化生态系统类型下土壤微生物的数量有所不同,其中单位重量土壤真菌数量 (cfu/g)多少顺序为：栓皮栎林(Quercus variabilis forest)＞马尾松林( Pinus massoniana forest)＞马尾松-栓皮栎混交林( Pinus massoniana-Quercus variabilis forest)＞杉木林( Cunninghamia lanceolata forest),细菌数量顺序为：马尾松-栓皮栎混交林( Pinus massoniana-Quercus variabilis forest)＞栓皮栎林( Quercus　variabilis forest)＞马尾松林( Pinus massoniana forest)＞杉木林( Cunninghamia lanceolata forest)。真菌种类鉴定表明,青霉菌(Penicillium ssp.)、镰刀菌(Fusarium spp.)、木霉菌(Trihoderma spp.)和葡萄孢菌(Botrytis spp.)等是组成该地区土壤真菌的主要类群。     

养殖中后期高位池对虾水体微生物群落结构及水体理化因子

针对凡纳滨对虾(Litopenaeus vannamei)高位池越冬棚养殖模式,采集养殖中后期水样,分析水体微生物群落结构、优势菌种类和水体理化因子的动态变化。结果表明:越冬棚保温效果良好,池塘水温由搭棚前最低的20.6℃上升并维持稳定于26.5℃左右,可满足对虾正常生长需求;养殖中后期水体异养细菌数量在5.10×104~2.95×105cfu·m L~(-1)波动,菌群结构相对稳定,优势菌数量在养殖后期略有增加;嗜冷杆菌(Psychrobacter)、亚硫酸杆菌(Sulfitobacter)等在养殖中后期均为优势种,搭棚后黄杆菌(Flavobacteria)、生丝微菌(Hyphomicrobium)等形成优势;亚硝氮、硝氮和水温是影响养殖中后期水体微生物群落分布的主要理化因子。研究表明,搭建越冬棚有利于保持养殖池塘水环境的相对稳定,养殖中后期水体氮素水平的控制尤为重要。因此,为促进水中有益菌的生态优势,调控水体菌群结构和生态功能,建议在养殖中后期,尤其是搭建越冬棚前后合理使用益生菌制剂,净化水质,稳定生态环境。     

三种海水生态养殖池塘细菌数量特征及其与环境因子的相关性

为阐明不同生态养殖池塘浮游细菌数量变化规律及其与环境因子间的相关性,以期为多元立体综合养殖模式中的水质安全与生物疾病防控提供科学依据。利用荧光显微镜细菌计数法(Acridine Orange Direct Counting),研究了“参-虾”“蟹-蛏”和“蜇-蛏”三种海水生态养殖池塘的细菌数量特征,使用典范对应分析(Canonical Correspondence Analysis, CCA)探讨细菌数量与环境因子的相互关系。结果表明,“参-虾”“蟹-蛏”和“蜇-蛏”池塘的细菌平均密度分别为(0.49～3.32)×10⁵ cell/mL、(0.52～2.98)×10⁵ cell/mL和(0.47～2.55)×10⁵ cell/mL,细菌数量有明显的时间差异,夏季密度大于春秋季。三种海水生态养殖池塘的水温、溶解氧和pH变化均不明显,且相差不大,而硝态氮均发生显著变化;其中“蟹-蛏”和“蜇-蛏”池塘的硝态氮、亚硝态氮、活性磷、总氮和总磷均高于“参-虾”池塘,透明度、叶绿素a和化学耗氧量则均低于“参-虾”池塘。典范对应分析(C...     

青岛近海及其临近海域冬季微微型浮游植物的分布

微微型浮游植物（0.2～2.0 μm） 是海水中最小的自养浮游生物, 在世界各海域广泛分布, 并在海洋有机物质循环中起着非常重要的作用.利用荧光显微技术对青岛近海及其邻近海域冬季微微型浮游植物丰度进行了调查,研究了微微型浮游植物的空间变化和昼夜变化的特征, 并分析了微微型浮游植物丰度与环境因子的相关性. 结果显示, 冬季该海域以富含藻红素（Phycoerythrin-rich, PE）的聚球藻(Synechococcus, Syn)细胞占优势,微微型真核藻类（Picoeukaryote, Euk）次之,而富含藻蓝素（Phycocyanin-rich, PC）的聚球藻细胞数量很低, 未发现原绿球藻（Prochlorococcus, Pro）的存在.Syn 的变化范围为8.97×10³～1.95×10⁵ cells·ml^-1, 平均4.67×10⁴ cells·ml^-1; Euk的变化范围为1.95×10²～1.01×10⁴ cells·ml^-1, 平均2.39×10³ cells·ml^-1. Syn丰度在胶南以南海域出现高值区域, 在即墨海域和崂山东南海域出现低值区域. Euk丰度在日照海域出现高值区域; 崂山海域为低值区域; 各水层Syn和Euk丰度均无明显差异(P﹥0.05). 对胶州湾中部连续站4层水体的24 h昼夜连续变化进行观测发现, Syn、Euk丰度都有明显昼夜波动.相关性分析表明： Syn与温度、 电导率呈正相关, 与溶氧浓度呈显著负相关; Euk与盐度和溶氧浓度呈显著负相关. 微微型浮游植物对总浮游植物生物量的贡献约为20％.     

Effect of probiotics on bacterial population and health status of shrimp in culture pond ecosystem

The artificially manufactured probiotics having beneficial bacteria, Bacillus spp. was applied regularly in a modified extensive shrimp (Penaeus monodon) culture pond, located on the bank of Vellar estuary, Parangipettai. The populations of total heterotrophic bacteria (THB), beneficial bacteria (Bacillus spp.) and pathogenic bacteria (vibrios) were monitored in water and sediment of the pond. The results were compared with a control pond, situated in the same location having same water spread area, stocking density, species managed with same technologies and optimum environmental parameters in which no probiotic was applied. The populations of THB and Bacillus spp. in the experimental pond increased and the vibrios decreased after each application of probiotics. But the result of the control pond showed an increasing trend of the populations of THB, Bacillus spp. and vibrios towards days of culture. The control pond had lower levels of THB and Bacillus spp. and higher levels of vibrios than the probiotic applied (experimental) pond. Also the probiotics maintained optimum transparency and low organic load in the experimental pond as compared to control. In general, water and sediment had almost equal number of Bacillus spp. and vibrios, but sediment had higher THB load than water. The applications of probiotics lesser pathogenic vibrios and enhance beneficial bacilli in the culture leading to improved water quality, promoted growth and survival rates and increased the health status of the shrimp without stress and disease outbreaks. Thus the application of probiotics could lead to disease-free and profitable shrimp culture operations which will be helpful for shrimp farmers as most of them are now-a-days severely affected by microbial diseases.     

长江口低氧区异养细菌及氮磷细菌分布

2009年8月15-28日,对长江口低氧高发海域的异养细菌、无机磷细菌、有机磷细菌、反硝化细菌和氨化细菌的空间分布特征进行初步研究.结果表明:氨化细菌数量最高,表层水、底层水和表层沉积物的数量均值分别为307.52×104个·L-1、184.50×104个·L-1和199.97×102个·g-1;其次为异养细菌,数量均值分别为87.35×104 cfu·L-1、86.85×104cfu·L-1和64.26×102cfu·g-1;再次为有机磷细菌,数量均值分别为19.26×104 cfu·L-1、18.82×104cfu·L-1和19.56×102cfu·g-1;无机磷细菌只分布在长江口内和河口南槽至舟山海域,数量均值分别为18.50×104cfu·L-1、31.00×104cfu·L-1和7.17×102cfu·g-1;反硝化细菌分布广,但数量较低,均值分别为3.94×104个·L-1、23.08×104个·L-1和6.22×102个·g-1.相关性分析结果说明:盐度、硝酸盐、磷酸盐、硅酸盐和pH是影响水体和表层沉积物异养细菌、磷细菌和反硝化细菌分布的主要因子;底层水和表层沉积物异养细菌、磷细菌与水温呈显著正相关;底层水异养细菌和有机磷细菌与溶解氧(DO)呈显著正相关;表层沉积物无机磷细菌与DO呈显著正相关,氨化细菌与DO呈显著负相关.聚类分析结果说明:低氧对表层沉积物的细菌群落结构产生影响.     

硝化细菌对加州鲈池塘水质影响及底质净化作用

为研究有益菌硝化细菌(Nitrifying bacteria)对加州鲈(Micropterus salmoides)高密度养殖池塘水质及底质的影响,在模拟加州鲈高密度养殖池塘单独施用硝化细菌,通过检测养殖水体pH、氨氮(NH4+-N)、亚硝酸盐氮、总氮(TN)及总磷(TP)等水质指标,底质沉积物中有机物、全氮及全磷等指标以及池塘浮游动植物量,以评价硝化细菌处理对加州鲈高密度养殖水体水质影响及底质净化作用。结果表明,硝化细菌能够稳定养殖水体pH,降低水体亚硝酸盐氮浓度,减缓养殖水体TN浓度上升,去除底质沉积物中有机物及全磷含量,有机物去除率达54.17%,全磷去除率达43.34%。硝化细菌处理前期浮游动植物总量高于对照池塘,后期逐渐减少并趋于稳定。     

Characterization of lactic acid bacteria isolated from the one humped camel milk produced in Morocco

One hundred and twenty (120) strains of lactic acid bacteria (LAB) were enumerated and isolated from raw dromedary milk in Morocco using various cultured media. Strains isolated were characterized by phenotypic, physiological and biochemical properties. Results showed that high counts of LAB were found. Presumptive lactobacilli counts ranged from 2.5x10(2) to 6x10(7)cfu/ml, presumptive lactococci levels varied from 5x10(2) to 6x10(7)cfu/ml, presumptive streptococci counts varied from 4.2x10(2) to 8x10(7)cfu/ml, presumptive leuconostoc levels ranged from 5.4x10(2) to 5.4x10(7)cfu/ml. Results showed also that Lactobacillus and Lactococcus were the predominant genera with 37.5% and 25.8%, respectively. The dominated species found were Lactococcus lactis subsp. lactis (17.5%), Lactobacillus helveticus (10%), Streptococcus salivarius subsp. thermophilus (9.20%), Lactobacillus casei subsp. casei (5.80%) and Lactobacillus plantarum (5%). This is the first report on the characterization of LAB strains isolated from the one humped camel milk produced in Morocco.     

Effect of probiotic bacteria on survival and growth of Cortez oyster larvae, Crassostrea corteziensis (Bivalvia: Ostreidae)

Disease control problems have major constraints in aquaculture production, and the use of probiotics in larviculture is a valid alternative to antibiotics. This study analyzed the effect of probiotic bacteria on survival and final size of Cortez oyster larvae Crassostrea corteziensis. Two different probiotic concentrations were evaluated, 1 x 10(4) and 1 x 10(5) CFU/ml of Lactic acid bacteria (strain NS61) isolated from Nodipecten subnodosus, and bacilli isolated from the white leg shrimp, Litopenaeus vannamei (Pseudomonas aeruginosa, strain YC58) and C. corteziensis (Burkholderia cepacia, strain Y021). Bacteria were added directly into culture tanks, starting the bioassays from veliger to pediveliger stages as follows: (1) Control, without probiotics; (2) lactic acid bacteria (Lb); (3) bacilli mix (Mb) in a proportion 1:1. Results showed a higher larval survival with Lb and Mb at a dose of 1 x 10(4) CFU/ml compared to the control group. Larvae exposed to Mb at 1 x 10(5) CFU/ml showed higher survival than Lb and control. Larval final size was not significantly increased with the tested probiotics, but larvae treated with Lb at 1 x 10(5) CFU/ml showed less survival rate than those treated at 1 x 10(4) CFU/ml. This study showed the beneficial effect of these probiotics, added individually or mixed in C. corteziensis larvae culture.     

缢蛏滩涂养殖环境的细菌群落组成及分析

1引言滩涂贝类养殖由于实行生态养殖,目前已成为宁波市海水养殖业的一大热点.近几年来,随着沿海经济的高速发展,滩涂环境污染问题日趋严重,养殖贝类大规模死亡的现象时有发生,给海洋水产经济造成了严重损失.而微生物数量及种群分布与区域环境有着密切联系,它可直接或间接地反映区域环境的营养水平、污染程度及底质状况等.目前有关养殖环境微生物学的研究主要是针对水体及养殖池底泥中的细菌[1,4,7～10],而对养殖滩涂环境细菌的研究很少[15,18,19].为此,本文以宁波市昆亭缢蛏滩涂养殖区为研究对象,从细菌生态学角度对滩涂缢蛏养殖环境进行研…     

Gilthead seabream (Sparus aurata L.) innate immune response after dietary administration of heat-inactivated potential probiotics

The effects of the dietary administration of two heat-inactivated whole bacteria from the Vibrionaceae family, singly or combined, on innate immune response of the seabream were studied. The two bacteria (Pdp11 and 51M6), which were obtained from the skin of gilthead seabream, showed in vitro characteristics that suggested they could be considered as potential fish probiotics. The fish were fed four different diets: control (non-supplemented), or diets supplemented with heat-inactivated bacteria at 10(8) cfu g(-1) Pdp11, 10(8) cfu g(-1) 51M6 or with 0.5 x 10(8) cfu g(-1) Pdp11 plus 0.5 x 10(8) cfu g(-1) 51M6 for 4 weeks. Six fish were sampled at weeks 1, 2, 3 and 4, when the main humoral (natural haemolytic complement activity and serum peroxidase content) and cellular innate immune responses (leucocyte peroxidase content, phagocytosis, respiratory burst and cytotoxicity) were evaluated. The serum peroxidase content and the natural haemolytic complement activity increased with time, reaching the highest values in the third and fourth weeks of feeding, respectively. The phagocytic ability of specimens fed the mixture of the two inactivated bacteria was significantly higher than in the controls after 2 and 3 weeks of treatment. The same activity increased significantly in seabream fed the Pdp11 diet for 2 weeks or the 51M6 diet for 3 weeks. Respiratory burst activity was unaffected by all the experimental diets at all times assayed. Cytotoxic activity had significantly increased after 3 weeks in fish fed the 51M6 diet. These results are discussed in terms of the usefulness of incorporating inactivated probiotic bacteria into fish diets.     

High concentration cultivation of Bifidobacterium bifidum in a submerged membrane bioreactor

In batch cultures, after 25 h, the maximum cell mass of Bifidobacterium bifidum BGN4 was 4.5 g/L, and the maximum cell count was 3.0 x 10(9) cfu/mL at pH 6.0 and 50 g/L sucrose. To increase the viable counts of bifidobacteria, cell retentive culture was applied using a submerged membrane bioreactor with suction and gas sparging. The maximum mass, count, and productivity of the cells after 36 h were 12.0 g/L, 2.2 x 10(10) cfu/mL, and 6.1 x 10(8) cfu/mL x h, respectively, at the feeding (dilution) rate of 120 mL/h (0.06 h-1) in the feeding medium. The accumulated levels of organic acids and ammonium ions at the end of the cultivation were 1.5 and 1.0 g/L, respectively. The viable counts and volumetric productivity of the cells after the cell retentive culture were 7.3- and 5.1-fold higher, respectively, than the values obtained during batch culture. These high viable counts and volumetric productivities were obtained by maintaining lower concentrations of organic acids and ammonium ions so that the growth of B. bifidum BGN4 was not inhibited. The submerged membrane bioreactor produced the highest viable counts of B. bifidum without membrane fouling and cell damage.     

汕头牛田洋沿海围垦区锯缘青蟹病害爆发的环境因素

锯缘青蟹(Scylla serrata)是汕头市的传统特色和优势养殖品种,也是拥有3万多亩海水养殖池塘的牛田洋围垦区的主养品种。近年来,每年9-11月份,牛田洋的青蟹病害严重,经济损失较大。为探讨青蟹发病与养殖环境的关系,于2007年4月至12月份对牛田洋养殖区的水体理化因子和生物因子进行连续监测研究,结果发现:各因子呈现出明显的季节性变化。在发病前的7-8月份,青蟹处于较高水温(≥28℃)和较低盐度(≤6)环境中。在发病期(9-11月份),各种环境因子恶化,其中铵态氮(NH4+-N)和亚硝态氮(NO2--N)在9月份达到峰值,分别为235.63μg·L-1和27.75μg·L-1;硝态氮(NO3--N)(10.85μg·L-1)、无机磷(PO34—P)(39μg·L-1)及生物因子(水体异养菌157.93×105cfu·L-1、弧菌116.75×103cfu·L-1,干重底泥异养菌157.93×105cfu·g-1、弧菌141.65×103cfu·g-1)在10月份达到峰值。结果说明:水体理化因子的恶化和条件致病微生物的大量增生是青蟹病害爆发的重要原因。     

Microbial communities in the saturated groundwater environment II: Diversity of bacterial communities in a Pleistocene sand aquifer and their in vitro activities

Bacterial cell numbers obtained from 103 water and sediment samples from a Pleistocene sandy aquifer in the Lower Rhine region (Bocholt, FRG) were determinated on P-agar and by direct count. Below 5 m under the surface, colony-forming unit (cfu) numbers in water samples were less than 100/ml, and in many cases less than 50/ml. In sediment samples, they were 10- to 100-fold higher (10²–10⁴ cfu/g dry wt), but changing markedly between different depths. Direct cell counts yielded numbers two to three orders of magnitude higher.About 2,700 strains of bacteria from 60 samples were isolated randomly and characterized by morphological and physiological properties. Of all the isolates, 71.6% were gram-negative, and 52.2% were gram-negative straight rods. Water communities, with one exception, had low proportions of gram-positive bacteria (<11%), whereas in all but one of the sediment communities percentages of gram-positive isolates were three- to sevenfold higher (35–43%). Water and sediment communities, as well as communities from different sampling sites and communities from different depths of the same sampling site, differed in their qualitative and quantitative morphotype composition and physiological capabilities.The in vitro activities of strains within a single community were quite different, indicating that each community is composed of many diverse bacteria, several having extremely different capabilities. Thus, each community has its own specific activity pattern. Gram-positive bacteria showed on an average lower total activities than did gram-negative bacteria. Grampositive bacteria as well as gram-negative bacteria from sediment had higher values of in vitro activities than the corresponding groups isolated from water. Many water and sediment bacteria preferred the same substrates which were utilized at high rates. However, there were differences in the degradation of the various other substrates present, and each community showed preferences for particular substrates, which they degraded best.The results of cell morphology and physiology studies indicated that all eight characterized communities were very different from one another and very diversely structured.