Relationship between size of parent at cell division and relative size of its progeny in Escherichia coli

This article examines the empirical basis for the assumption of independence between the relative size (length or surface area) of a newborn cell w and the absolute size of its mother at cell division. Random samples from two strains of Escherichia coli B/r cells in steady-state exponential growth, covering a range of doubling times, were fixed in osmium tetroxide and prepared for electron microscopy by agar filtration. Length and diameter of over 3000 constricted cells were measured from the electron micrographs and cell surface area computed by assuming an idealized geometry of right circular cylinders with hemispherical polar caps. In general, these strains were found to divide into two daughter cells with a precision that is independent of the size of the mother. In addition, both a normal and a symmetrical beta-distribution were shown to fit the observed size distributions of w rather well; theoretical grounds for preferring the latter are discussed.     

Spontaneous zygogenesis (Z-mating) in mecillinam-rounded bacteria

In Escherichia coli the process of spontaneous zygogenesis (Z-mating), i.e. complete genetic mixing in the absence of a conjugative plasmid, was investigated further. Spontaneous-zygogenesis-promoting (Szp⁺) cells displayed strong clustering with each other and with ordinary F⁻ cells in the optimal cell density range for Z-mating. When induced to rounding by the drug mecillinam, they aggregated into large, dense, stainable syncytium-like cells leaving giant ghosts upon lysis. In Z-mating mixtures of mecillinam-treated cells, these giant cells co-purified with mating products as other cells died. Giant cells recovering from mecillinam treatment yielded monstrous, branching forms, whereas non-Szp⁺ coccal cells reverted to rods in one step, and some 29% of the colonies formed were identified as deriving from entities possessing two distinct genomes. Z-mating was examined between E. coli and a distantly related Serratia marcescens strain. In the presence of calcium, mecillinam-rounded cells of a stable non-complementing diploid hybrid with the E. coli phenotype segregated normally dividing cells of the Serratia form.     

The growth kinetics ofB. subtilis

There has been considerable discussion by Kubitschek and Cooper concerning the growth rate of cells ofE. coli throughout the cell cycle. Consequently, it is relevant to test Kubitschek's linear model against the exponential model espoused by Cooper (and many others) with another organism and another technique.Burdett et al. measured, by electron microscopy and computer analysis of the microphotographs, the distribution of lengths of a population of cells ofBacillus subtilis grown in 0.4% succinate in a minimal medium. The data were fitted to the extended Collins-Richmond method of Kirkwood & Burdett which subdivided the cell cycle into several phases. I have taken their results and compared them with the linear and exponential growth models for the entire cell cycle after applying correction to the data for the shape of completed and forming poles; i.e., to put the data on a cell-volume basis instead of a cell-length basis. Most of the correction involves no arbitrary assumptions. The conclusion is that global volume growth rate is nearly proportional to cell volume; i.e. growth ofBacillus subtilis is nearly exponential for almost every cell in the growing culture.     

Light and electron microscopic study on the endocrine cells of the pancreas in a marine teleost,Fugu rubripes rubripes

Summary The pancreatic endocrine tissue of Fugu rubripes rubripes consists of numerous round principal islets (Brockmann bodies) of various sizes scattered around the gall-bladder. The endocrine cells are divided into A-, B-, D-, and F_f-cells. Each cell type was identified by comparing thick and thin sections in both light and electron microscopy. Aldehyde-fuchsin positive B-cells contain numerous round secretory granules (average diameter 300 nm) each of which has a round compact core of moderate density; a narrow space exists between this core and the limiting membrane. Grimelius' silver positive A cells contain round secretory granules (average diameter 360 nm) with a hexagonal or tetragonal crystalline core (average diameter 170 nm) of high density; the silver grains preferentially appear in the space between the limiting membrane and the core. The crystalline core of each -granule often contains an appendix-like structure of variable shape. D cells blackened by the silver impregnation method of Hellman and Hellerström (1960) have round secretory granules (average diameter 320 nm) filled with a flocculent material of low density. The fourth cell type (F_f-cell) has a clear cytoplasm after differential staining for light microscopy. By electron microscopy, this cell has elongated fusiform secretory granules (520 nm average length × 230 nm average width) filled with numerous filaments arranged in parallel with the longitudinal axis. Figures suggesting granule formation in the sacs of the Golgi apparatus were obtained in all of islet cell types. Equivalents of emiocytotic release of secretory granules were encountered in the A and F_f cells.     

优良单株家系辣木叶的表型性状分析

为挖掘辣木(Moranga oleifera)优良种质资源,对30个优良单株家系的叶片表型性状进行研究。结果表明,除叶形外,辣木不同家系间的叶柄和叶片颜色、复叶数、复叶柄长度和直径、复叶间距、叶长、叶宽均存在不同程度的差异。复叶数与复叶柄长度和直径、复叶间距、叶长、叶宽呈极显著正相关;主成分分析表明,叶长、叶宽、复叶柄长度和直径、复叶间距、叶柄和叶片颜色是区分辣木不同家系最主要的叶片性状指标。聚类分析结果表明,30个辣木家系可分为3大类,叶片表型性状存在显著差异的家系的遗传距离较远。因此,叶柄和叶片颜色、复叶数、复叶柄长度和直径、复叶间距、叶长、叶宽将为直观区分辣木家系提供参考。     

The efficacy of Scenedesmus morphology as a defense mechanism against grazing by selected species of rotifers and cladocerans

Phytoplankton often develop various defense mechanisms in response to zooplankton grazing, such as spines and colonies. While it is now known that increased spine length and cells in a colony of members of the genus Scenedesmus, when zooplankton grazing is intense, helps in reducing zooplankton filtering rates, the effect of these defense mechanisms at the population level has been observed in few studies. Here we present data on the growth rates of four zooplankton species, Brachionus calyciflorus, B. patulus, Ceriodaphnia dubia and Daphnia pulex at two food levels using two species of colony-forming Scenedesmus spp.: S. acutus (cell length = 18.2 ± 0.4 µm; width = 4.2 ± 0.1 µm; average colony length = 90 µm; width: 21 µm) and S. quadricauda (cell length: 21 ± 0.5 width 7.5 ± 0.3 µm; average colony length: 84 µm; width: 30 µm). Whereas S. acutus had no spines, S. quadricauda had spines of 6–10 µm. Population growth experiments of the test rotifers and cladocerans were conducted in 100 ml containers with 50 ml of the medium with test algae. Algae concentrations used were: 13 and 52 mg dw l^–1 of each of the two algal species offered in colonial forms. We used an initial inoculation zooplankter density of 1 ind. ml^–1 for either of the rotifer species and 0.2 ind. ml^–1 for either of the cladoceran species. In all, we had 64 test containers (4 test species of zooplankton × 2 test species of algae × 2 algal densities × 4 replicates). We found a significant effect of algal size on the growth rates of all the four tested species of zooplankton. The population growth rates of zooplankton ranged from –0.58 to 0.66 and were significantly higher on diet of S. acutus than of S. quadricauda. Thus, our study confirms that the larger colony size and the formation of spines in S. quadricauda were effective defenses against grazing by both rotifers and smaller sized cladoceran Ceriodaphnia dubia but that larger-bodied Daphnia pulex could exploit both the algal populations equally.     

苦豆子表型性状多样性分析及综合评价

该研究以自然分布的内蒙、宁夏、甘肃、新疆、陕西等23个不同地理来源(种源)的野生苦豆子种子及其播种于内蒙古鄂托克前旗同质园内的当年生植株为材料,采用方差分析、主成分分析、聚类分析等方法对种子长、宽、千粒重以及植株的叶长、叶宽、叶面积、叶形指数、苗高、地径及生物量等10个表型性状的多样性进行了研究。结果表明:各个表型性状种源间均呈极显著差异,其中种子表型性状的变异系数为5.24%,植株表型性状的变异系数为18.34%,表明种子性状的稳定性高于植株性状。同时,10个性状的表型分化系数均高于70%,说明苦豆子表型多样性主要来源于种源间的表型变异;各种源苦豆子种子性状的表型分化系数均值高达97.55%,且种长、千粒重分别与采集地经度、纬度和海拔等环境因子呈极显著相关性,说明种子表型性状受环境因素的影响较大;相关性分析显示,苦豆子植株性状叶长(LL)、叶面积(LA)分别与种子性状千粒重(TW)、种长(SL)和种宽(SW)有显著相关性,暗示表型性状中的可遗传变异影响;利用主成分和聚类分析对23个种源苦豆子进行综合评价,筛选出生物量较大、苗高较高、千粒重较重、叶面积较大等综合表现较好的6个种源,共分为两类,分别是DK、JY、WY、WH、ETK和YN,这为苦豆子种质资源定向开发以及选育和栽培提供了一定的理论支撑和基础材料。     

Starvation survival of Gordonia polyisoprenivorans CCT 7137, isolated from contaminated groundwater in Brazil

Gordonia polyisoprenivorans CCT7137, exopolysaccharide-producing bacterium, was isolated from groundwater contaminated with leachate in a former municipal landfill site (São Paulo, Brazil). The strain was submitted to starvation in phosphate-buffered saline solution for 56 days so as to evaluate its behavior regarding cuturability and cell morphology. As a response to starvation, G. polyisoprenivorans CCT7137 presented reduction in viable cell count, cell size and cell shape alteration. The initial number of viable cells was 1.51 × 10⁷ c.f.u. ml. After 7 days of starvation culturability dropped to 13.70% (2.07 × 10⁶ c.f.u/ml) and, after 56 days, to 3.25% (4.93 × 10⁵ c.f.u/ml). It was also observed that after 7 days of starvation the cell size presented an average reduction in the values of length, length/width ratio, volume and area of 50, 58, 40 and 42%, respectively. The length/width ratio showed a change of shape from rod to coccobacillus. Changes in cell dimensions and distribution of cell into classes were not significant after day 7 of starvation. The results obtained show that it is not necessary for the strain to starve for more than a week to obtain G. polyisoprenivorans CCT7137 size- reduced cells. The results also indicate the potential for its starved forms to be used in future tests in porous medium to study the production of exopolysaccharide in situ.     

Quantitative analysis of time-series fluorescence microscopy using a spot tracking method: application to Min protein dynamics

The dynamics of MinD protein has been recognized as playing an important role in the accurate positioning of the septum during cell division. In this work, spot tracking technique (STT) was applied to track the motion and quantitatively characterize the dynamic behavior of green fluorescent protein-labeled MinD (GFP-MinD) in an Escherichia coli system. We investigated MinD dynamics on the level of particle ensemble or cluster focusing on the position and motion of the maximum in the spatial distribution of MinD proteins. The main results are twofold: (i) a demonstration of how STT could be an acceptable tool for MinD dynamics studies; and (ii) quantitative findings with parametric and non-parametric analyses. Specifically, experimental data monitored from the dividing E. coli cells (typically 4.98 ± 0.75 μm in length) has demonstrated a fast oscillation of the MinD protein between the two poles, with an average period of 54.6 ± 8.6 s. Observations of the oscillating trajectory and velocity show a trapping or localized behavior of MinD around the polar zone, with average localization velocity of 0.29 ± 0.06 μm/s; and flight switching was observed at the pole-to-pole leading edge, with an average switching velocity of 2.95 ± 0.31 μm/s. Subdiffusive motion of MinD proteins at the polar zone was found and investigated with the dynamic exponent, α of 0.34 ± 0.16. To compare with the Gaussian-based analysis, non-parametric statistical analysis and noise consideration were also performed. Co-first authors     

Direct and indirect interactions for coexistence in a species-defined microcosm

Mechanisms for coexistence among micro-organisms were studied by using a species-defined microcosm, consisting of the bacterium Escherichia coli, the ciliate Tetrahymena thermophila and the alga Euglena gracilis. These organisms were chosen as representative of ecological functional groups i.e. decomposer, consumer and producer, respectively. Direct and indirect interactions among these organisms were evaluated by comparisons of their population dynamics in culture with different combinations of the three species. There was an E. coli cell density dependent predator–prey interaction between T. thermophila and E. coli which was only established when there were more than 10⁶ cells ml^–1 of E. coli. Indirect interactions were evaluated from the cultivation of each organism in media containing metabolites of the others. Metabolites from each population strongly accelerated the growth of their own populations and those of the others except for the self-toxicity effect of E. coli metabolites. These observations suggested that not only the cell–cell contact of direct interactions, but also metabolite-mediated indirect interactions supported the maintenance of the populations of each micro-organism and their coexistence. In natural ecosystems, there are many interactions and it is difficult to evaluate all those regulating community dynamics. The gnotobiotic microcosm used in this study was shown to be suitable for examining the specific, species–species microbial interactions.     

Effects of chemically and electrochemically dosed chlorine on Escherichia coli and Legionella beliardensis assessed by flow cytometry

The present study reports the disinfection effects of chemically and electrochemically dosed chlorine on two models for typical water-borne bacteria (Escherichia coli and Legionella beliardensis) by plating and flow cytometry (FCM) in combination with different fluorescence dyes. The residual effect on various cell functions, including cultivability, esterase activity, membrane polarization, and integrity, was tested at different free chlorine concentrations. In comparison, chemical disinfection yielded on average 60% more E. coli cells entering the viable but nonculturable (VBNC) state than electrochemical disinfection. Here, VBNC is defined as those cells with intact cell membrane but which cannot be cultured on solid nutrient agar plates. L. beliardensis was about five times more resistant to chlorine disinfection than E. coli. The results also suggested the two methods result in different disinfection mechanisms on L. beliardensis, i.e., chemically dosed chlorine targeted cell membrane integrity before enzyme activity, while electrochemically dosed chlorine acted the other way round. In addition, both bacteria lost the integrity of their cell membranes at three times lower chlorine concentration over a longer contact time (i.e., 40 vs. 10 min) by the chemical method. Our results showed that FCM is an appropriate tool to evaluate the effects of water disinfection and the percentage of cells in VBNC in a matter of hours. Electrochemical disinfection is suggested to be a favorable alternative for chemical disinfection.     

Structure and possible function(s) of charasomes; complex plasmalemma-cell wall elaborations present in some characean species

Summary Charasomes, complex membrane structures, were found along the longitudinal walls of internodal and lateral branch cells ofChara corallina andC. braunii, but not along their transverse walls or in other cell types. Charasome-complexes were larger and more numerous in the lateral branch cells than in internodal cells. InC. corallina, a dioecious species, especially large elaboration of charasome material occurs in the lateral branch cells of the female plant, sometimes reaching a cross-sectional width which is as great as that of the adjacent cell wall. Chara internodes transport hydroxyl (OH^–) out of the cell and bicarbonate (HCO₃ ^–) into the cell. Spatial distribution of charasomes along the cell was examined with respect to these transport phenomena, which occur at specific identifiable regions along the cell. Charasome-complexes were always found in regions in which HCO₃ ^– transport occurs but were often fewer, reduced in size or absent in areas of OH^– efflux.Nitella flexilis exhibited similar patterns of OH^– and HCO₃ ^– transport along the cell; however, there was a complete absence of charasomes. Ultrastructural examinations onNitella translucens indicated that charasomes were also absent in this species. The observation that charasomes are present in both transport regions ofChara but are totally lacking in the twoNitella spp. indicates that the charasome-complex is not involved in transport of either substance. Other possible functions for the charasomes, including a role in osmoregulation, are discussed.Charasome substructure is the same in bothChara species, consisting of a mass of short (50 nm average length) anastomosing tubules (30 nm average diameter) derived from the plasmalemma. The interior of the tubules is open to the cytoplasm while the area surrounding the tubules is ultimately open to the wall and thus can be considered to be wall space. Charasomes are quite variable in size and shape, but are roughly globular, with the bulk of the structure projecting into the cell cytoplasm. Tubular components of the charasome were sometimes seen to extend into the microfibrillar wall matrix. A three dimensional model of the charasome-complex presented details the great complexity of this membrane system.     

The regulation of tooth morphogenesis is associated with epithelial cell proliferation and the expression of Sonic hedgehog through epithelial-mesenchymal interactions

Ectodermal organs, such as the tooth, salivary gland, hair, and mammary gland, develop through reciprocal epithelial–mesenchymal interactions. Tooth morphologies are defined by the crown width and tooth length (macro-morphologies), and by the number and locations of the cusp and roots (micro-morphologies). In our current study, we report that the crown width of a bioengineered molar tooth, which was reconstructed using dissociated epithelial and mesenchymal cells via an organ germ method, can be regulated by the contact area between epithelial and mesenchymal cell layers. We further show that this is associated with cell proliferation and Sonic hedgehog (Shh) expression in the inner enamel epithelium after the germ stage has formed a secondary enamel knot. We also demonstrate that the cusp number is significantly correlated with the crown width of the bioengineered tooth. These findings suggest that the tooth micro-morphology, i.e. the cusp formation, is regulated after the tooth width, or macro-morphology, is determined. These findings also suggest that the spatiotemporal patterning of cell proliferation and the Shh expression areas in the epithelium regulate the crown width and cusp formation of the developing tooth.     

Spermatogenesis in goats with and without scrotum bipartition

The objective of the present research was to quantify the seminiferous epithelium cells, spermatogenesis efficiency and characterize the ultrastrucure of Sertoli cells in goats. Eighteen goats were used and divided into three groups: Group I - goats without bipartition of the scrotum; Group II - animals with bipartition of the scrotum in up to 50% of the testicular length; Group III - goats with bipartition of the scrotum in more than 50% of the testicular length. The goat testes in Group III had a greater number of primary spermatocytes (25.37 ± 4.55 cells per cross sections), spermatids (112 ± 15.12 cells per cross sections), and Sertoli cells (9.46 ± 1.74 cells per cross sections) than the animals in Groups I and II (P<0.05). The spermatogenic mitotic, meiotic, and general efficiency were greater in animals in Group III (1.25 ± 0.28; 5.12 ± 1.63; 6.44 ± 1.96) when compared to those in Groups I and II. Sheet-like processes originated from the Sertoli cell body as simple and smooth structures which involved almost all the surface of germ cells. Slender cord-like processes originated from Sertoli cells and also from the sheet-like processes. The relative frequency of the cycle stages showed differences among the groups of goats studied, and the highest frequency was in Stage 3 (20.68% for goats in Group I, 21.15% for those in Group II, and 16.89% for the animals in Group III). In conclusion, goats with bipartition of the scrotum have a greater number of germ and Sertoli cells per cross section of seminiferous tubule, that indicated a greater sperm production when compared to the other groups, and the ultrastructure of the Sertoli cell process did not present any relationship with bipartition of the scrotum.     

Breeding of an elite <Emphasis Type="Italic">Laminaria</Emphasis> variety 90-1 through inter-specific gametophyte crossing

Laminaria longissima and Zaohoucheng No.1 (a commercial variety selected from Laminaria japonica) differ to a certain extent in their morphological characteristics and biological habits. It was assumed that varieties bred through their hybridization should exhibit high yield potential and tolerate relatively high seawater temperatures. Female gametophyte clones isolated from L. longissima were crossed with male clones isolated from Zaohoucheng No.1. Laminaria variety 90-1 was obtained after gametophyte crossing, continuous self-crossing and selection. This variety was genetically homozygous; the indices of variation of blade length, width and thickness of the final two selection cycles were 7–8%; i.e., not different significantly. Variety 90-1 grew faster, lost less tissue and had higher yield potential than two widely used commercial varieties of L. japonica (all commercial varieties currently used in China originate from this latter species). The blade of variety 90-1 increased 3.71 cm day⁻¹ on average during the whole period of cultivation, almost two-fold that of two controls, and growth was maintained even when seawater temperature was higher than 18°C–3°C higher than the temperature tolerated by other Laminaria varieties. Variety 90-1 increased yield by more than 70% over two controls and also synthesized desirable amounts of iodine, mannitol and algin. In blade length, variety 90-1 was more similar to L. longissima than to L. japonica, but more similar to L. japonica in blade width and thickness. Since the adoption of variety 90-1 in 1999, its culturing area has increased each year to reach its current area of 7,000 ha, i.e., almost one-third of the total cultivation acreage of Laminaria in China. Breeding of variety 90-1 has demonstrated that it is feasible to develop elite Laminaria varieties by crossing gametophytes from different Laminaria species in combination with successive self-crossing and selection.     

Über die Abgrenzung derChlorosarcinales von denChlorococcales

It is proposed to use amongst other characters the type of cell division in order to delimit theChlorosarcinales from theChlorococcales. A definition of the two processes of division occuring in these orders is given. It differs from that of other authors. In theChlorosarcinales only those genera should be assembled in which vegetative daughter cells arise by bipartition followed by firm association of the wall between the daughter cells with that of the mother cell. In contrast, autospores, the vegetative daughter cells of a number ofChlorococcales, develop by multiple division, their cell walls are formed all around the protoplasts and are free from that of the mother cell. The chlorococcalean generaTrebouxia andDictyochloropsis incorporate species which multiply by zoo-, aplano- and autospores as well as others having no autospores. Autospores possibly have arisen more than once during evolution.

     

Cell shape and microtubules in zoospores of the green algaChlorosarcinopsis gelatinosa (Chlorosarcinales): Effects of low temperature

Summary The effect of low temperature (2 °C) on cell shape and microtubules in zoospores of the green algaChlorosarcinopsis gelatinosa has been investigated. The zoospores are 4–6 times longer than wide with a mean length of 12,5 m and can be kept in the dark for several hours without changes in cell shape. Cell shape changes have been evaluated quantitatively by measuring changes in cell length. Low temperature induces a decrease in cell length which exhibits a two-step kinetic: during the first 30 minutes a rapid rate of decrease in cell length was measured, while during the next 4 hours a slow rate of decrease in cell length was observed. Complete regeneration of zoospore length occurs when cold-treated cells are subjected to the original zoospore induction temperature (30 °C) for two hours. Observation of numbers, disposition and types of microtubules in the zoospore during decrease in cell length has shown that within 30 minutes after cold application the secondary cytoskeletal microtubules (scmt) disappear, while flagellar root microtubules are unaffected. During this period most cells develop a prominent posterior appendage (tail). Sections demonstrate the presence of several microtubules in these tails. Flagellar root microtubules probably extend into the tails and disappearance of scmt starts at the posterior pole of the cell. Regeneration of zoospores to original cell length is coupled with reappearance of scmt starting at the anterior pole of the cell. It is concluded that secondary cytoskeletal microtubules constitute the main cytoskeleton inChlorosarcinopsis zoospores and that flagellar root microtubules contribute to only a minor extent to the cytoskeleton, because they cannot retain the cell shape. The results are discussed with respect to the functional significance of flagellar root microtubules in green algae.     

A cluster of cell division genes maps to the terC region of the chromosome of Escherichia coli K-12

Thirty-nine cell division mutants were isolated in Escherichia coli K-12 and were mapped in the terminus region of the chromosome, between 33.5 and 36 min. They were obtained by two different approaches involving specific mutagenesis of the terC region. The mutants could be divided into eight classes (I to VIII) based on their map position and phenotype at the restrictive temperature, and constitute a new cell division gene cluster.     

Biomass relationship to growth and phosphate uptake ofPseudomonas fluorescens,Escherichia coli andAcinetobacter radioresistens in mixed liquor medium

The ability ofPseudomonas fluorescens, Escherichia coli andAcinetobacter radioresistenns to remove phosphate during growth was related to the initial biomass as well as to growth stages and bacterial species. Phosphate was removed by these bacteria under favourable conditions as well as under unfavourable conditions of growth. Experiments showed a relationship between a high initial cell density and phosphate uptake. More phosphate was released than removed when low initial cell densities (10²–10⁵ cells ml^–1) were used. At a high initial biomass concentration (10⁸ cells ml^–1), phosphate was removed during the lag phase and during logarthmic growth byP. fluorescens. Escherichia coli. at high initial biomass concentrations (10⁷ cells ml^–1), accumulated most of the phosphate during the first hour of the lag phase and/or during logarithmic growth and in some cases removed a small quantily of phosphate during the stationary growth phase.Acinetobacter radioresistens, at high initial cell densities (10⁶, 10⁷ cells ml^–1) removed most of phosphate during the first hour of the lag phase and some phosphate during the stationary growth phase.Pseudomonas fluorescens removed phosphate more thanA. radioresistens andE. coli with specific average ranges from 3.00–28.50 mg L^–1 compared to average ranges of 4.92–17.14 mg L^–1 forA. radioresistens and to average ranges of 0.50–8.50 mg L^–1 forE. coli.     

Expression of antimicrobial peptide LH multimers in <Emphasis Type="Italic">Escherichia coli</Emphasis> C43(DE3)

The tandem repeats of LFB15(W4,10)-HP(4-16) (LH) gene were cloned into vector pET32a(+) for recombinant expression in Escherichia coli. The E. coli C43(DE3) was successfully used as the expression host to avoid the cell death during induction in E. coli BL21(DE3). Fusion LH dimer was expressed as inclusion body at a portion of 35% of total cell protein and could be well purified by Ni²⁺-chelating chromatography. The recombinant LH was released by the cleavage of 50% formic acid, and its yield reached 11.3 mg/l with purity of 95%. The MIC₅₀ of 3.6 and 1.9 μM of recombinant LH against E. coli CMCC 44102 and Bacillus subtilis ATCC 6633 were determined, respectively. The results demonstrated that expression of tandem LH gene in E. coli C43(DE3) and formic acid cleavage would provide a potent efficient platform for the production of interested peptides. Zi-gang Tian and Tian-tang Dong contributed equally to this paper.