A novel genus of multicellular magnetotactic prokaryotes from the Yellow Sea

Multicellular magnetotactic prokaryotes (MMPs) are a group of magnetotactic microorganisms composed of 10-40 Gram-negative cells. Currently, all the identified MMPs show a spherical morphology and synthesize mainly iron sulfide magnetosomes. In this study, we report a novel genus of MMPs with peculiar ellipsoidal morphology and iron oxide magnetosomes, which were discovered in intertidal sediment of the Yellow Sea in China. Optical and fluorescence microscopy revealed that this organism was ~10 × 8 μm in size and composed of ~40 cells enveloped by an outer layer. Scanning electron microscopy showed that the cells were arranged in 4-6 interlaced circles. Bullet-shaped magnetite magnetosomes were organized in chains roughly parallel to the long axis of the ellipsoidal MMPs when analysed by transmission electron microscopy. These MMPs displayed special escape motility, i.e. swimming rapidly from the edge to the centre of the droplet and then slowly back to the edge. In addition, they exhibited negative phototaxis. Light microscopy observations showed that the ellipsoidal MMPs reproduced by division along the body long axis. Both analysis of 16S rRNA gene sequence and fluorescence in situ hybridization revealed the ellipsoidal MMPs as a new genus of the Deltaproteobacteria. In summary, this novel genus of MMPs exhibit unique morphology, peculiar division process and distinct phylogenetic affiliation compared with the other MMPs.     

Isolation and characterization of a magnetotactic bacterial culture from the Mediterranean Sea

The widespread magnetotactic bacteria have the peculiar capacity of navigation along the geomagnetic field. Despite their ubiquitous distribution, only few axenic cultures have been obtained worldwide. In this study, we reported the first axenic culture of magnetotactic bacteria isolated from the Mediterranean Sea. This magneto‐ovoid strain MO‐1 grew in chemically defined O₂ gradient minimal media at the oxic–anoxic transition zone. It is phylogenetically related to Magnetococcus sp. MC‐1 but might represent a novel genus of Proteobacteria. Pulsed‐field gel electrophoresis analysis indicated that the genome size of the MO‐1 strain is 5 ± 0.5 Mb, with four rRNA operons. Each cell synthesizes about 17 magnetosomes within a single chain, two phosphorous‐oxygen‐rich globules and one to seven lipid storage granules. The magnetosomes chain seems to divide in the centre during cell division giving rise to two daughter cells with an approximately equal number of magnetosomes. The MO‐1 cell possesses two bundles of seven individual flagella that were enveloped in a unique sheath. They swam towards the north pole with a velocity up to 300 μm per second with frequent change from right‐hand to left‐hand helical trajectory. Using a magneto‐spectrophotometry assay we showed that MO‐1 flagella were powered by both proton‐motive force and sodium ion gradient, which is a rare feature among bacteria.     

Magnetosome chain arrangement and stability in magnetotactic cocci

We have studied the disposition of chains of magnetosomes inside magnetotactic cocci with light and electron microscopy. Light microscopy of isolated cocci indicated that the chains of magnetosomes are disposed on opposite sides of the cell. Electron spectroscopic imaging of whole unprocessed bacteria, showed the magnetosome chains in the cells. Freeze-etching of the cell surface allowed the observation of the close association of the chain with the cell surface. During the replication process of the freeze-etching, the magnetosome chains remained attached to the replicas, which indicates that chains were very close to the cell surface before freezing. We provide evidence that the large area of the contact faces between magnetosomes in a chain may provide an extra mechanical stability that helps keep the magnetosomes in chains even after isolation from the bacteria. Comparison with pointed magnetosomes from different cocci present in the same samples showed that the maintenance of linear chains is more difficult to be achieved because of the geometry of the crystals.     

A novel species of ellipsoidal multicellular magnetotactic prokaryotes from Lake Yuehu in China

Two morphotypes of multicellular magnetotactic prokaryotes (MMPs) have been identified: spherical (several species) and ellipsoidal (previously one species). Here, we report novel ellipsoidal MMPs that are ～ 10 × 8 μm in size, and composed of about 86 cells arranged in six to eight interlaced circles. Each MMP was composed of cells that synthesized either bullet‐shaped magnetite magnetosomes alone, or both bullet‐shaped magnetite and rectangular greigite magnetosomes. They showed north‐seeking magnetotaxis, ping‐pong motility and negative phototaxis at a velocity up to 300 μm s^?1. During reproduction, they divided along either their long‐ or short‐body axes. For genetic analysis, we sorted the ellipsoidal MMPs with micromanipulation and amplified their genomes using multiple displacement amplification. We sequenced the 16S rRNA gene and found 6.9% sequence divergence from that of ellipsoidal MMPs, Candidatus Magnetananas tsingtaoensis and > 8.3% divergence from those of spherical MMPs. Therefore, the novel MMPs belong to different species and genus compared with the currently known ellipsoidal and spherical MMPs respectively. The novel MMPs display a morphological cell differentiation, implying a potential division of labour. These findings provide new insights into the diversity of MMPs in general, and contribute to our understanding of the evolution of multicellularity among prokaryotes.     

Envelope ultrastructure of uncultured naturally occurring magnetotactic cocci

Magnetotactic bacteria are microorganisms that respond to magnetic fields. We studied the surface ultrastructure of uncultured magnetotactic cocci collected from a marine environment by transmission electron microscopy using freeze-fracture and freeze-etching. All bacteria revealed a Gram-negative cell wall. Many bacteria possessed extensive capsular material and a S-layer formed by particles arranged with hexagonal symmetry. No indication of a metal precipitation on the surface of these microorganisms was observed. Numerous membrane vesicles were observed on the surface of the bacteria. Flagella were organized in bundles originated in a depression on the surface of the cells. Occasionally, a close association of the flagella with the magnetosomes that remained attached to the replica was observed. Capsules and S-layers are common structures in magnetotactic cocci from natural sediments and may be involved in inhibition of metal precipitation on the cell surface or indirectly influence magnetotaxis.     

中华鲟外周血细胞组成及形态观察

利用光镜和透射电镜技术对北京海洋馆养殖的40尾中华鲟(Acipenser sinensis)(介于4—30龄以上, 包括野生、子一代和子二代共7个龄组)外周血细胞组成、大小、显微和超微结构进行研究。结果表明, 在外周血细胞中可区分出以下六类细胞。形态结果: 红细胞卵圆形, 胞质内可见少量线粒体; 淋巴细胞多圆形, 有明显伪足样或指状胞凸, 核质比大, 可明显分为大淋巴和小淋巴; 嗜中性粒细胞核型多样, 胞质细胞器丰富, 含有大小不等的特殊颗粒; 嗜酸性粒细胞多为规则圆形, 表面大量细小指状突起, 胞质细胞器丰富, 含有大量个体较大的嗜酸性颗粒; 单核细胞变形现象多, 胞质内大量空泡, 核型多样; 血栓细胞形状多样, 胞质内大量小的空泡, 散布或成团出现, 常见直接分裂现象。各类血细胞从大到小依次为: 单核细胞、嗜中性粒细胞、嗜酸性粒细胞、大淋巴细胞、红细胞、血栓细胞和小淋巴细胞, 各龄组间无显著差异。外周血红细胞总数(RBC)平均为(5.56±1.19)×108/mL, 18龄和11龄与其他龄组之间存在显著性差异(P<0.05); 白细胞总数(WBC)平均为(16.53±4.94)×106/mL, 18龄与4龄间存在显著差异, 且分别与其他龄组间存在显著性差异(P<0.05); 血栓细胞总数(15.53±15.82)×106/mL。白细胞分类计数(DLC)中大淋巴细胞、小淋巴细胞、嗜中性粒细胞、嗜酸性粒细胞和单核细胞所占百分比分别为: (5.26±3.95)%、(77.74±11.73)%、(9.40±7.98)%、(1.90±2.06)%、(5.50±4.00)%, >30龄和4龄间显著差异, 且分别与其他龄组间存在显著性差异( P<0.05)。结论认为中华鲟血细胞进化地位低, 免疫系统为淋巴细胞系为主, 主要包括淋巴细胞、粒细胞和单核细胞, 结果对中华鲟的健康评价与保育研究有重要的参考意义。     

A simple and accurate method for quantification of magnetosomes in magnetotactic bacteria by common spectrophotometer

A simple apparatus for measuring the magnetism of magnetotactic bacteria was developed with a common laboratory spectrophotometer, which was based on measuring the change in light scattering resulting from cell alignment in a magnetic field. A multiple coils were built around the cuvette holder of the spectrophotometer to compensate geomagnetic field and to generate two mutually perpendicular magnetic fields. In addition, we defined a novel magnetism parameter, R(mag), by modifying the definition of C(mag) to a normalized parameter with the culture absorbance obtained without application of magnetic field. The number of magnetosomes in each cell was determined by transmission electron microscopy to assess the relationship between the two magnetism parameters and the distribution of magnetosomes in the cells. We found that both R(mag) and C(mag) were linearly correlated rather with the percentage of magnetosome-containing bacteria than with the average magnetosome numbers, and R(mag) exhibited a better linearity than C(mag) with respect to the percentage of magnetosome-containing bacteria.     

Grazing protozoa and magnetosome dissolution in magnetotactic bacteria

Magnetotactic bacteria show an ability to navigate along magnetic field lines because of magnetic particles called magnetosomes. All magnetotactic bacteria are unicellular except for the multicellular prokaryote (recently named 'Candidatus Magnetoglobus multicellularis'), which is formed by an orderly assemblage of 17-40 prokaryotic cells that swim as a unit. A ciliate was used in grazing experiments with the M. multicellularis to study the fate of the magnetosomes after ingestion by the protozoa. Ciliates ingested M. multicellularis, which were located in acid vacuoles as demonstrated by confocal laser scanning microscopy. Transmission electron microscopy and X-ray microanalysis of thin-sectioned ciliates showed the presence of M. multicellularis and magnetosomes inside vacuoles in different degrees of degradation. The magnetosomes are dissolved within the acidic vacuoles of the ciliate. Depending on the rate of M. multicellularis consumption by the ciliates the iron from the magnetosomes may be recycled to the environment in a more soluble form.     

趋磁细菌生态学研究进展

趋磁细菌是一类革兰氏阴性的原核生物,广泛分布于淡水和海水环境中的有氧-无氧过渡区.趋磁细菌的分布与其环境中的氧、硫化物及铁等的浓度相关,不同种类分布在不同的物化梯度范围内.趋磁细菌的生长、磁小体的合成及磁小体的成分对环境有一定程度的指示作用.它们在生物地球化学循环中起着重要的作用.主要针对以上研究内容进行回顾,同时结合本实验室的一些研究结果做初步的分析,并对趋磁细菌生态学研究进行展望.     

东海剧毒卡尔藻的形态特征及其系统进化分析

利用光学显微镜、荧光显微镜、扫描电镜及分子生物学等方法, 对分布于我国东海海域的剧毒卡尔藻（Karlodinium veneficum）藻株（LAMB090611）的形态特征和显微结构进行了描述, 并探讨了其分子系统进化关系。该藻株细胞长11.1-18.7 μm, 平均值为（14.2±1.8） μm, 宽8.2-14.7 μm, 平均值为（10.8±1.5） μm。细胞形态结构特征为： 上下锥体积基本相同; 顶沟短而直; 腹孔明显; 纵沟延伸至上锥; 横沟错位距离约占细胞总长的28%-38%; 含有2或4个不规则形态的叶绿体; 细胞核位于中部或下锥。此藻种的暴发可引发有害赤潮（harmful algal bloom）。当前加强有害赤潮的预防和监测工作是减少危害的有效途径, 而对引发赤潮原因种的准确识别和鉴定则是基础和关键。     

海城碘泡虫(黏体动物门，黏孢子纲)补充描述及基于18S rDNA系统发育分析

海城碘泡虫原始描述中形态数据较为简单,且存在多个宿主及寄生部位,其有效性有待确定。利用现行主流的黏孢子虫形态特征和基因标记系统分析相结合的分类学方法,对采自太湖棒花鱼鳃丝的海城碘泡虫进行了补充描述。该碘泡虫孢囊呈白色,圆形,大小为(0.6—1.1) mm。成熟孢子正面观近似椭圆形,上端稍尖,侧面观呈纺锤型,孢子长(10.8±0.7) μm (10.1—11.5 μm),孢子宽:(8.1±0.5) μm (7.5—9.0 μm),孢子厚:(5.7±0.4) μm (5.2—9.0 μm);两极囊呈梨形,大小存在细微差别,极囊顶端存在突起,大极囊长:(4.7±0.5) μm (4.8—6.7 μm),宽:(2.5±0.2) μm (3.2—4.3 μm),小极囊长:(4.4±0.2) μm (4.1—4.8 μm),宽:(2.2±0.1) μm (2.0—2.5 μm);极丝盘绕4—5圈。基于18S rDNA序列(GenBank登录号:KY965936)比对分析,该碘泡虫与放射孢子虫Hexactinomyxon type 2相似率最高,为97%。系统发育分析表明,该碘泡虫与Hexactinomyxon type 2、Hexactinomyxon type 1、Hexactinomyxon type SH-2006、Myxobolus pfeifferi、Myxobolus caudatus和Myxobolus squamae聚为独立分支,和其他已报道的黏孢子虫亲缘关系较远。研究在补充了海城碘泡虫形态学、基因标记序列信息基础上,推断了该虫生活史。     

Isolation of magnetotactic bacterium WM-1 from freshwater sediment and phylogenetic characterization

The magnetotactic bacterium was isolated from freshwater sediment from North Lake of Wuhan. The isolate, designated WM-1, was Gram-negative, helical shaped, and studied by means of electron microscopy. The strain WM-1 was 0.2-0.4 μm in diameter and 3–4 μm in length. The DNA G + C content was found to be 65.7 mol%. Phylogenetic analysis of the 16S rDNA gene (Accession number DQ899734 in GeneBank) revealed that this isolate was a member ofαsubdivision of the Proteobacteria. Strain WM-1 was closely related (97.7%) to Magnetospirillum sp. AMB-1. Randomly amplified polymorphic DNA analysis showed that these two strains were in fact different strains. Electron diffraction patterns of WM-1 magnetosomes indicated that the magnetosomes were composed of magnetite. The magnetosomes from WM-1 were cuboidal in shape as observed by electron microscopy. Statistical analysis of magnetite crystals from WM-1 showed narrow asymmetric size distribution. The average number of magnetosomes in each WM-1 bacterium was 8 ± 3.4. The average length of magnetosomes in WM-1 was 54 ± 12.3 nm and the average width is 43 ± 10.9 nm. These data showed that the grains in WM-1 were single-domain crystals.     

Magnetosome chain superstructure in uncultured magnetotactic bacteria

Magnetotactic bacteria produce magnetosomes, which are magnetic particles enveloped by biological membranes, in a highly controlled mineralization process. Magnetosomes are used to navigate in magnetic fields by a phenomenon called magnetotaxis. Two levels of organization and control are recognized in magnetosomes. First, magnetotactic bacteria create a spatially distinct environment within vesicles defined by their membranes. In the vesicles, the bacteria control the size, composition and purity of the mineral content of the magnetic particles. Unique crystal morphologies are produced in magnetosomes as a consequence of this bacterial control. Second, magnetotactic bacteria organize the magnetosomes in chains within the cell body. It has been shown in a particular case that the chains are positioned within the cell body in specific locations defined by filamentous cytoskeleton elements. Here, we describe an additional level of organization of the magnetosome chains in uncultured magnetotactic cocci found in marine and freshwater sediments. Electron microscopy analysis of the magnetosome chains using a goniometer showed that the magnetic crystals in both types of bacteria are not oriented at random along the crystal chain. Instead, the magnetosomes have specific orientations relative to the other magnetosomes in the chain. Each crystal is rotated either 60°, 180° or 300° relative to their neighbors along the chain axis, causing the overlapping of the (1?1?1) and [Formula in text] capping faces of neighboring crystals. We suggest that genetic determinants that are not present or active in bacteria with magnetosomes randomly rotated within a chain must be present in bacteria that organize magnetosomes so precisely. This particular organization may also be used as an indicative biosignature of magnetosomes in the study of magnetofossils in the cases where this symmetry is observed.     

Ultrastructure,tactic behaviour and potential for sulfate reduction of a novel multicellular magnetotactic prokaryote from North Sea sediments

Multicellular magnetotactic prokaryotes (MMPs) represent highly organized, spherical and motile aggregates of 10–40 bacterial cells containing magnetosomes. Although consisting of different cells, each with its own magnetosomes and flagellation, MMPs orient themselves within a magnetic field and exhibit magnetotaxis. So far, MMPs have only been found in several North and South American coastal lagoons and salt marshes. In the present study, a novel type of MMP was discovered in coastal tidal sand flats of the North Sea. High‐resolution scanning electron microscopy revealed the presence of bullet‐shaped magnetosomes which were aligned in several parallel chains. Within each aggregate, the magnetosome chains of individual cells were oriented in the same direction. Energy dispersive X‐ray (EDX) analysis showed that the magnetosomes are composed of iron sulfide. This particular morphology and arrangement of magnetosomes has previously not been reported for other MMPs. 16S rRNA gene sequence analysis revealed a single phylotype which represented a novel phylogenetic lineage with ≥ 4% sequence divergence to all previously described MMP sequences and was related to the dissimilatory sulfate‐reducing Desulfosarcina variabilis within the family Desulfobacteraceae of the subphylum Deltaproteobacteria. Fluorescence in situ hybridization with a specific oligonucleotide probe revealed that all MMPs in the tidal flat sediments studied belonged to the novel phylotype. Within each MMP, all bacterial cells showed a hybridization signal, indicating that the aggregates are composed of cells of the same phylotype. Genes for dissimilatory sulfite reductase (dsrAB) and dissimilatory adenosine‐5′‐phosphate reductase (aprA) could be detected in purified MMP samples, suggesting that MMPs are capable of sulfate reduction. Chemotaxis assays with 41 different test compounds yielded strong responses towards acetate and propionate, whereas other organic acids, alcohols, sugars, sugar alcohols or sulfide did not elicit any response. By means of its coordinated magnetotaxis and chemotaxis, the novel type of MMP is well adapted to the steep chemical gradients which are characteristic for intertidal marine sediments.     

Insight into the assembly properties and functional organisation of the magnetotactic bacterial actin-like homolog, MamK

Magnetotactic bacteria (MTB) synthesize magnetosomes, which are intracellular vesicles comprising a magnetic particle. A series of magnetosomes arrange themselves in chains to form a magnetic dipole that enables the cell to orient itself along the Earth's magnetic field. MamK, an actin-like homolog of MreB has been identified as a central component in this organisation. Gene deletion, fluorescence microscopy and in vitro studies have yielded mechanistic differences in the filament assembly of MamK with other bacterial cytoskeletal proteins within the cell. With little or no information on the structural and behavioural characteristics of MamK outside the cell, the mamK gene from Magnetospirillium gryphiswaldense was cloned and expressed to better understand the differences in the cytoskeletal properties with its bacterial homologues MreB and acitin. Despite the low sequence identity shared between MamK and MreB (22%) and actin (18%), the behaviour of MamK monitored by light scattering broadly mirrored that of its bacterial cousin MreB primarily in terms of its pH, salt, divalent metal-ion and temperature dependency. The broad size variability of MamK filaments revealed by light scattering studies was supported by transmission electron microscopy (TEM) imaging. Filament morphology however, indicated that MamK conformed to linearly orientated filaments that appeared to be distinctly dissimilar compared to MreB suggesting functional differences between these homologues. The presence of a nucleotide binding domain common to actin-like proteins was demonstrated by its ability to function both as an ATPase and GTPase. Circular dichroism and structural homology modelling showed that MamK adopts a protein fold that is consistent with the 'classical' actin family architecture but with notable structural differences within the smaller domains, the active site region and the overall surface electrostatic potential.     

尖形碘泡虫(黏体门:碘泡虫科)的重描述及其分子系统学研究

研究基于形态和分子信息重描述了寄生于嘉陵江重庆段鲫(Carassius auratus Linnaeus)鳃部和胆囊的尖形碘泡虫(Myxobolus acutus Wu and Chen, 1987),并获得了该虫体的18S rDNA和ITS1 rDNA序列。尖形碘泡虫成熟孢子壳面观呈梨形,前端稍尖,后端钝圆,缝面观呈宽纺锤形。孢子长(13.6±0.9)μm [(11.4—15.3)μm],宽(10.2±0.9)μm [(7.5—12.8)μm],厚(7.6±0.6)μm [(6.9—8.3)μm]。两梨形极囊开口处紧靠并位于孢子前端,极囊大小不等,大极囊长(6.2±0.4)μm [(5.1—7.5)μm],宽(3.8±0.4)μm [(2.8—4.7)μm],极丝盘绕5—8圈,小极囊长(2.7±0.4)μm [(1.7—3.7)μm],宽(1.4±0.2)μm [(0.9—1.9)μm],极丝盘绕2—3圈。基于18S rDNA为分子标记的系统发育分析显示:尖形碘泡虫与中华单极虫(Thelohanellus sinensis)有最近的亲缘关系,两物种形成的进化支与贝壳碘泡虫(M. mu...     

Morphometric analysis of bacteria associated with soil millipedes

Scanning electron microscopy revealed that the average cell size of bacteria associated with the digestive tract of soil millipedes was 0.65 μm in diameter, 1.36 μm in length, and 0.60 μm³ in volume. An example of millipedes illustrated that the intestinal tract bacteria of soil invertebrates share the following features: (1) a high density level in this habitat; (2) existence mostly in the form of vegetative cells; (3) a cell size significantly smaller than that of bacteria functioning in soil; (4) a cell size closer to the lower limits of the size range characteristic for bacterial cultures grown in laboratory media. All this suggests that the bacterial community of the digestive tract differs from the typical soil community not only in composition but also in a higher level of physiological activity.     

Surface structure changes of rat adipocytes during lypolysis stimulated by various lypolysis stimulated by various lypolytic agents

A qualitative and quantitative electron microscopic study was performed on rat adipocytes during stimulation of lipolysis by various agents. Scanning electron microscopy of control cells revealed a spherical cell with a textured glycocalyx surface exhibiting small irregular projections. Globular surface evaginations or protrusions measuring 8-18 μM in diameter were seen on cell hemispheres, and there was an average of one protrusion for every two hemispheres examined. Distribution analysis showed that 60 percent of the hemispheres had no protrusions, and 25, 10, and 5 percent of the hemispheres had one, two or three protrusions, respectively. Thin-section and freeze- fracture electron microscopy of the protrusions showed a small triglyceride droplet surrounded by a thin cytoplasmic rim that was continuous with the main cytoplasmic matrix. The glycocalyx coating and plasma membrane extended from the cell surface onto, and over, the protrusion. Scanning microscopy of cells stimulated by lipolytic agents, including epinephrine, adrenocorticotropic hormone, theophylline, and dibutyryl cyclic AMP, revealed a dose-dependent increase in the number of protrusions per cell hemisphere. Maximal concentrations of lipolytic hormones cuase an average 2.5-fold increase in the number of protrusions per hemisphere without changing the average size of the protrusions. Only 40 percent of the stimulated cell hemispheres exhibited no protrusions; over 15 percent of the cells contained three or more; and a number of the protrusions were multilobulate. Insulin prevented the increase in the number of protrusions and the change in distribution caused by the lipolytic hormones but did not prevent the increase caused by theophylline and dibutryl cyclic AMP. The data suggest that the protrusions are a structural feature of the cell and may be related to the lypolytic pathway. These observations may help explain some of the discrepant biochemical data relating to hormonal stimulation of lipolysis.     

小梁切除术中应用丝裂霉素C 对角膜内皮细胞的影响

目的:观察小梁切除术中应用丝裂霉素C(MMC)对角膜内皮细胞的影响。方法:收集2010年9月2011年5月在我院行小梁切除术的青光眼患者60例(78眼),随机分为术中应用丝裂霉素C的36例(46眼)患者为A组,术中不用丝裂霉素C的24例(32眼)为B组,分别观察术前、术后1个月和术后3个月两组眼压(IOP)、角膜内皮细胞的密度(CD)、平均细胞面积(AVG)及细胞面积变异系数(CV),分析其数量的改变及两组间的差异。结果:A组术前眼压为(35.4±13.7)mmHg,B组术前眼压为(32.5±13.5)mmHg差异无统计学意义(P>0.05),A组术后1个月及术后3个月眼压分别为(15.7±3.7)mmHg、(17.0±3.2)mmHg,均低于B组的(19.4±3.7)mmHg、(20.2±2.1)mmHg,差异有统计学意义(P<0.05)。A组术前、术后1个月及术后3个月角膜内皮细胞密度分别为(2475±484)个/mm2、(2199±373)个/mm2、(2164±332)个/mm2;平均细胞面积分别为(431.4±67.6)μm2、(480.6±66.8)μm2、(463.8±46.2)μm2;细胞面积变异系数分别为(31.1±7.4)%、(34.4±6.3)%、(31.2±7.5)%;术后1个月及术后3个月各参数与术前比较,差异均有统计学意义(P<0.05)。B组术前、术后1个月及术后3个月角膜内皮细胞密度分别为(2342±94)个/mm2、(2185±215)个/mm2、(2074±218)个/mm2;平均细胞面积分别为(453.9±94.8)μm2、(516.3±100.8)μm2、(499.81±106.4)μm2;细胞面积变异系数分别为(30.2±3.0)%、(32.7±2.9)%、(31.4±4.3)%;除术后3个月角膜内皮细胞与术前比较有意义(P<0.05)外,余参数术后1个月及术后3个月与术前比较差异均无统计学意义(P>0.05)。术后1个月A组的角膜内皮细胞丢失率为10.4%高于B组的6.1%,差异有统计学意义(P<0.05);术后3个月A组的角膜内皮细胞丢失率为11.1%高于B组的10.0%,差异无统计学意义(P>0.05)。结论:小梁切除术中用丝裂霉素C的降压效果比不用丝裂霉素C的效果好,但短期内前者角膜内皮细胞的丢失率高于后者。