Population dynamics of Vibrio fischeri during infection of Euprymna scolopes

The luminous bacterium Vibrio fischeri colonizes a specialized light-emitting organ within its squid host, Euprymna scolopes. Newly hatched juvenile squid must acquire their symbiont from ambient seawater, where the bacteria are present at low concentrations. To understand the population dynamics of V. fischeri during colonization more fully, we used mini-Tn7 transposons to mark bacteria with antibiotic resistance so that the growth of their progeny could be monitored. When grown in culture, there was no detectable metabolic burden on V. fischeri cells carrying the transposon, which inserts in single copy in a specific intergenic region of the V. fischeri genome. Strains marked with mini-Tn7 also appeared to be equivalent to the wild type in their ability to infect and multiply within the host during coinoculation experiments. Studies of the early stages of colonization suggested that only a few bacteria became associated with symbiotic tissue when animals were exposed for a discrete period (3 h) to an inoculum of V. fischeri cells equivalent to natural population levels; nevertheless, all these hosts became infected. When three differentially marked strains of V. fischeri were coincubated with juvenile squid, the number of strains recovered from an individual symbiotic organ was directly dependent on the size of the inoculum. Further, these results indicated that, when exposed to low numbers of V. fischeri, the host may become colonized by only one or a few bacterial cells, suggesting that symbiotic infection is highly efficient.     

The fine structure of the leaf nodules of Ardisia crispa (Thunb.) A.DC. (Myrsinaceae)

The fine structure of the leaf nodules of Ardisia crispa is described. The bacterial endophyte in mature nodules is extracellular, forming a compact mass which is encompassed within a 5–6 cell thick sheath of modified mesophyll cells. Processes from these sheath cells invade the bacterial mass providing a host surface across which exchange of metabolites may take place. Considerable pleomorphism is exhibited by the bacteria, paralleling that found in other symbiotic associations in which the host can influence the morphology of the microsymbiont. The spherical, highly granate chloroplasts, rich in starch, which are characteristic of the spongy mesophyll leaf cells, are replaced, in the modified sheath cells, by a degenerate plastid form containing membrane whorls. Lipid reserves appear to replace the starch in the sheath cells. The significance of these changes is discussed.     

Vascular architecture in the bacteriogenic light organ of Euprymna tasmanica (Cephalopoda: Sepiolidae)

Symbiosis between southern dumpling squid, Euprymna tasmanica (Cephalopoda: Sepiolidae), and its luminescent symbiont, the bacterium Vibrio fischeri, provides an experimentally tractable system to examine interactions between the eukaryotic host and its bacterial partner. Luminescence emitted by the symbiotic bacteria provides light for the squid in a behavior termed “counter‐illumination,” which allows the squid to mask its shadow amidst downwelling moonlight. Although this association is beneficial, light generated from the bacteria requires large quantities of oxygen to maintain this energy‐consuming reaction. Therefore, we examined the vascular network within the light organ of juveniles of E. tasmanica with and without V. fischeri. Vessel type, diameter, and location of vessels were measured. Although differences between symbiotic and aposymbiotic squid demonstrated that the presence of V. fischeri does not significantly influence the extent of vascular branching at early stages of symbiotic development, these finding do provide an atlas of blood vessel distribution in the organ. Thus, these results provide a framework to understand how beneficial bacteria influence the development of a eukaryotic closed vascular network and provide insight to the evolutionary developmental dynamics that form during mutualistic interactions.     

The fine structure of the leaf nodules of Ardisia crispa (Thunb.) A.DC. (Myrsinaceae)

The fine structure of the leaf nodules of Ardisia crispa is described. The bacterial endophyte in mature nodules is extracellular, forming a compact mass which is encompassed within a 5–6 cell thick sheath of modified mesophyll cells. Processes from these sheath cells invade the bacterial mass providing a host surface across which exchange of metabolites may take place. Considerable pleomorphism is exhibited by the bacteria, paralleling that found in other symbiotic associations in which the host can influence the morphology of the microsymbiont. The spherical, highly granate chloroplasts, rich in starch, which are characteristic of the spongy mesophyll leaf cells, are replaced, in the modified sheath cells, by a degenerate plastid form containing membrane whorls. Lipid reserves appear to replace the starch in the sheath cells. The significance of these changes is discussed.     

阔叶杨桐衍生胎座的发育特征(五列木科)

为观察五列木科阔叶杨桐子房中衍生胎座的发育过程,探明衍生胎座与心皮源胎座及特立中央胎座的关系,该研究采用扫描电子显微镜和体视显微镜相结合的方法,详细观察了阔叶杨桐的花芽和成熟果实。花芽采集后经FAA固定、酒精-乙酸异戊酯梯度脱水、液体CO_2干燥、扫描电子显微镜下观察;将成熟果实直接在体视显微镜下解剖观察。结果表明:阔叶杨桐花芽发育过程中,雄蕊原基发生后,5心皮快速发生,先愈合形成上部具有中轴胎座、下部是空腔的子房;接着心皮上长出胎座(心皮源胎座),在其下部空腔内与心皮相对的位置,花托顶端出现多个凸起,并逐渐愈合成半球形的衍生胎座,心皮源胎座和衍生胎座上出现多枚可育胚珠。成熟果实中,心皮源胎座和衍生胎座上均有种子,二者之间没有维管束联系。因此,衍生胎座与心皮源胎座独立发生,且晚于心皮源胎座;阔叶杨桐衍生胎座的发育过程不同于石竹科和商陆科的特立中央胎座(中轴胎座隔膜消失形成),而与杜鹃花目报春花科、假轮叶科、杜茎山科和紫金牛科的特立中央胎座类似(在花托顶端直接形成)。     

Bacterial adaptation to life in association with plants - A proteomic perspective from culture to in situ conditions

Diverse bacterial taxa that live in association with plants affect plant health and development. This is most evident for those bacteria that undergo a symbiotic association with plants or infect the plants as pathogens. Proteome analyses have contributed significantly toward a deeper understanding of the molecular mechanisms underlying the development of these associations. They were applied to obtain a general overview of the protein composition of these bacteria, but more so to study effects of plant signaling molecules on the cytosolic proteome composition or metabolic adaptations upon plant colonization. Proteomic analyses are particularly useful for the identification of secreted proteins, which are indispensable to manipulate a host plant. Recent advances in the field of proteome analyses have initiated a new research area, the analysis of more complex microbial communities. Such studies are just at their beginning but hold great potential for the future to elucidate not only the interactions between bacteria and their host plants, but also of bacteria-bacteria interactions between different bacterial taxa when living in association with plants. These include not only the symbiotic and pathogenic bacteria, but also the commensal bacteria that are consistently found in association with plants and whose functions remain currently largely uncovered.     

棉花变异体(CHV1)的花形态特征分析

棉花体细胞培养再生植株存在大量的生理变异和可遗传变异,从中分离到一个性状稳定的花器变异体(CHV1)。从花器官形态特征和表面显微特征分析,该变异体的所有花器官都变成了苞叶状器官,但中央数片叶状器官的基部有胎座和胚珠着生。变异体每朵花有苞叶3-7片,苞叶状器官19-41片。苞叶状器官在花梗上的排布介于“轮”与“螺旋”状之间。据花器发育理论和变异体花的生长特性推测,该变异体中控制花器发育的A、B和C功能皆失活。对造成该变异的可能机理和棉花花发育模式进行了分析。该变异材料对研究棉花花发育和体细胞无性系变异的机理有一定价值。     

Population Dynamics of Vibrio fischeri during Infection of Euprymna scolopes

The luminous bacterium Vibrio fischeri colonizes a specialized light-emitting organ within its squid host, Euprymna scolopes. Newly hatched juvenile squid must acquire their symbiont from ambient seawater, where the bacteria are present at low concentrations. To understand the population dynamics of V. fischeri during colonization more fully, we used mini-Tn7 transposons to mark bacteria with antibiotic resistance so that the growth of their progeny could be monitored. When grown in culture, there was no detectable metabolic burden on V. fischeri cells carrying the transposon, which inserts in single copy in a specific intergenic region of the V. fischeri genome. Strains marked with mini-Tn7 also appeared to be equivalent to the wild type in their ability to infect and multiply within the host during coinoculation experiments. Studies of the early stages of colonization suggested that only a few bacteria became associated with symbiotic tissue when animals were exposed for a discrete period (3 h) to an inoculum of V. fischeri cells equivalent to natural population levels; nevertheless, all these hosts became infected. When three differentially marked strains of V. fischeri were coincubated with juvenile squid, the number of strains recovered from an individual symbiotic organ was directly dependent on the size of the inoculum. Further, these results indicated that, when exposed to low numbers of V. fischeri, the host may become colonized by only one or a few bacterial cells, suggesting that symbiotic infection is highly efficient.     

The functional morphology of the organs of feeding and digestion of the hydrothermal vent bivalve Calyptogena magnifica (Vesicomyidae)

The discovery, around Galapagos Rift hydrothermal vents, of an unique community of animals dependent upon the chemoautotrophic oxidation of hydrogen sulphide by bacteria, has aroused wide interest. In the gutless pogonophoran Riftia pachyptila. trophosomal symbiotic bacteria are thought to be principally responsible for this unique form of nutrition. Similar symbiotic bacteria have been postulated for the ctenidia of the Rift clam Calyptogena magnifica. Such a mode of nutrition was deemed necessary since Calyptogena was thought not to possess ctenidial food grooves, thereby making normal filter-feeding impossible. This study reports upon the anatomy of a specimen of C. magnifica and demonstrates the presence of narrow ctenidial food grooves and the normal bivalve complement of feeding and digestive organs. Using a variety of general bacterial and DNA specific stains, no evidence of symbiotic intracellular bacteria has been found in the ctenidia (or any other tissues). It is concluded that C. magnifica is principally a filter feeder, albeit with modification for collecting and processing a diet of bacterial cells, with the possibility (as in all bivalves) of direct absorption. High chemoautotrophic activity levels in the ctenidia probably result from entrapment of vent water bacteria collected during filter feeding.     

The Inductive Role of Bacterial Symbionts in the Morphogenesis of a Squid Light Organ

SYNOPSIS. The association of the sepiolid squid Euprymna scolopeswith its marine luminous bacterial symbiont Vibrio fischeriis an emerging model system to study the initiation and developmentof bacterial symbioses in higher animals, in particular theinfluence of bacteria on the ontogenic development of symbiotic-specifichost tissues. Experiments comparing the development of juvenilesquid infected with symbiotic V. fischeri with that of uninfectedjuveniles suggest postembryonic development of the light organrequires cell-cell interactions with the bacterial symbionts.The presence of symbiotic bacteria induces specific morphologicalchanges by affecting such fundamental processes as cell deathand cell differentiation. The surface of the juvenile organis largely composed of ciliated cells that appear to facilitateinfection of the light organ. These cells begin to undergo celldeath within hours of infection with symbiotic V. fischeri.Within three days the epithelial cells that form the bacteriacontainingcrypts of the light organ increase in size; these cells do notappear mitotically active, and may represent a terminally differentiatedstate. The light organs of uninfected juvenile E. scolopes,however, do not exhibit any of these early postembryonic developmentalevents but remain in a state of arrested morphogenesis.     

棉花变异体（CHV1）的花形态特征分析

棉花体细胞培养再生植株存在大量的生理变异和可遗传变异,从中分离到一个性状稳定的花器变异体(CHV1)。从花器官形态特征和表面显微特征分析,该变异体的所有花器官都变成了苞叶状器官,但中央数片叶状器官的基部有胎座和胚珠着生。变异体每朵花有苞叶3—7片,苞叶状器官19—41片。苞叶状器官在花梗上的排布介于“轮”与“螺旋”状之间。据花器发育理论和变异体花的生长特性推测,该变异体中控制花器发育的A、B和C功能皆失活。对造成该变异的可能机理和棉花花发育模式进行了分析。该变异材料对研究棉花花发育和体细胞无性系变异的机理有一定价值。     

Single-plant,Sterile Microcosms for Nodulation and Growth of the Legume Plant Medicago truncatula with the Rhizobial Symbiont Sinorhizobium meliloti

Rhizobial bacteria form symbiotic, nitrogen-fixing nodules on the roots of compatible host legume plants. One of the most well-developed model systems for studying these interactions is the plant Medicago truncatula cv. Jemalong A17 and the rhizobial bacterium Sinorhizobium meliloti 1021. Repeated imaging of plant roots and scoring of symbiotic phenotypes requires methods that are non-destructive to either plants or bacteria. The symbiotic phenotypes of some plant and bacterial mutants become apparent after relatively short periods of growth, and do not require long-term observation of the host/symbiont interaction. However, subtle differences in symbiotic efficiency and nodule senescence phenotypes that are not apparent in the early stages of the nodulation process require relatively long growth periods before they can be scored. Several methods have been developed for long-term growth and observation of this host/symbiont pair. However, many of these methods require repeated watering, which increases the possibility of contamination by other microbes. Other methods require a relatively large space for growth of large numbers of plants. The method described here, symbiotic growth of M. truncatula/S. meliloti in sterile, single-plant microcosms, has several advantages. Plants in these microcosms have sufficient moisture and nutrients to ensure that watering is not required for up to 9 weeks, preventing cross-contamination during watering. This allows phenotypes to be quantified that might be missed in short-term growth systems, such as subtle delays in nodule development and early nodule senescence. Also, the roots and nodules in the microcosm are easily viewed through the plate lid, so up-rooting of the plants for observation is not required.     

FLORAL ONTOGENY IN CYCLAMEN PERSICUM ‘F-1 ROSEMUNDE ROSE’ (PRIMULACEAE)

Floral ontogeny was examined in Cyclamen persicum ‘F-1 Rosemunde Rose’ using a combination of light and scanning electron microscopy. The leaf plastochron index (LPI), earlier calculated for leaf elongation, was used to determine the length of each stage of floral development. LPI will provide a useful tool for selecting flowers of a given stage from large plant populations or from plants where flowers are small or inaccessible during early ontogenetic stages. Most features of floral development are similar to those previously described for other primulaceous genera. The petal-stamen relationship, however, is unusual; stamens arise through periclinal cell divisions in the adaxial surface layers of common petal-stamen primordia. Anatomical evidence suggests that the placenta is formed both by appendicular initials which give rise to the ovules and ventral carpellary bundles, and receptacular cells which form some, if not all, of the central axis.     

Adaptation of the Brucellae to their intracellular niche

Members of the bacterial genus Brucella are facultative intracellular pathogens that reside predominantly within membrane-bound compartments within two host cell types, macrophages and placental trophoblasts. Within macrophages, the brucellae route themselves to an intracellular compartment that is favourable for survival and replication, and they also appear to be well-adapted from a physiological standpoint to withstand the environmental conditions encountered during prolonged residence in this intracellular niche. Much less is known about the interactions of the Brucella with placental trophoblasts, but experimental evidence suggests that these bacteria use an iron acquisition system to support extensive intracellular replication within these host cells that is not required for survival and replication in host macrophages. Thus, it appears that the brucellae rely upon the products of distinct subsets of genes to adapt successfully to the environmental conditions encountered within the two cell types within which they reside in their mammalian hosts.     

Comparative microbiome analysis of Diaphorina citri and its associated parasitoids Tamarixia radiata and Diaphorencyrtus aligarhensis reveals Wolbachia as a dominant endosymbiont

Microbiome analysis in a host–parasitoid interaction network was conducted to compare the taxonomic composition of bacterial communities of Diaphornia citri, Tamarixia radiata, and Diaphorencyrtus aligarhensis. The comparative analysis revealed differences in the composition and diversity of the symbiont populations across the host and its associated parasitoids. Proteobacteria was the most dominant phylum, representing 67.80% of the total bacterial community, while Candidatus Profftella armature and Wolbachia were the dominant genera across the host and parasitoids. There were clear differences observed in alpha and beta diversity of microbiota through the host and its associated parasitoids. The function prediction of bacterial communities and Pearson correlation analysis showed that specific bacterial communities displayed positive correlations with the carbohydrate metabolism pathway. Furthermore, when symbiotic bacteria were eliminated using a broad-spectrum antibiotic, tetracycline hydrochloride, the parasitoids' median survival time and longevity were significantly reduced. We confirmed the physiological effects of symbiotic bacteria on the fitness of parasitoids and demonstrated the effect of antibiotics in decreasing the food intake and measurement of amino acids in the hemolymph. This study sheds light on basic information about the mutualism between parasitoids and bacteria, which may be a potential source for biocontrol strategies for citrus psyllid, especially D. citri.     

Floral development of Iris decora Wall. (Iridaceae)

The outer tepal and stamen primordia arise as secondary primordia on the outer tepal-stamenprimordia, which are formed on the floral apex. The inner tepal primordia are formed directly on the floral apex. All the floral appendages are initiated in the second tunica layer and are homologous with regard to their origin and early development. A short perianth tube is formed as a result of intercalary growth in the common bases of the tepal primordia. The intercalary growth in the fused bases of the floral appendages elevates the peripheral zone. The floral apex thus appears as a shallow cup. Further intercalary growth results in the formation of an inferior ovary. The ovules are initiated as outgrowths on placental ridges from the lateral ovary wall, the trilocular appearance being the result of secondary cohesion of the parietal placentae.     

How endo- is endo-? Surface sterilization of delicate samples: a <Emphasis Type="Italic">Bryopsis</Emphasis> (Bryopsidales,Chlorophyta) case study

In the search for endosymbiotic bacteria, elimination of ectosymbionts is a key point of attention. Commonly, the surface of the host itself or the symbiotic structures are sterilized with aggressive substances such as chlorine or mercury derivatives. Although these disinfectants are adequate to treat many species, they are not suitable for surface sterilization of delicate samples. In order to study the bacterial endosymbionts in the marine green alga Bryopsis, the host plant’s cell wall was mechanically, chemically and enzymatically cleaned. Merely a chemical and enzymatic approach proved to be highly effective. Bryopsis thalli treated with cetyltrimethylammonium bromide (CTAB) lysis buffer, proteinase K and bactericidal cleanser Umonium Master showed no bacterial growth on agar plates or bacterial fluorescence when stained with a DNA fluorochrome. Moreover, the algal cells were intact after sterilization, suggesting endophytic DNA is still present within these algae. This new surface sterilization procedure opens the way to explore endosymbiotic microbial communities of other, even difficult to handle, samples.     

Animal-Bacterial Interactions in the Early Life History of Marine Invertebrates: The Euprymna scolopes/Vibrio fischeri Symbiosis

SYNOPSIS. The symbiotic association between the Hawaiian sepiolidsquid Euprymna scolopes and the marine luminous bacterium Vibriofischeri is being developed as a model system for the studyof animal-bacterial interactions during development. Changesin light organ morphology during embryogenesis foster successfulinfection of the light organ with the proper bacterial partner.These embryonic events of light organ morphogenesis includethe elaboration of an epithelial surface with a complex ciliated,microvillous field. The squid host hatches without the bacterialsymbionts, but acquires them within hours from the free-livingpopulation of the bacteria in the water column. Upon exposureto the proper symbionts, the host organ undergoes a series ofmorphogenetic changes, including loss of the ciliated, microvillousfield. The light organ then goes on to mature into a morphologicalconfiguration that serves to promotethe maintenance of a stableassociation with the bacteria and that correlates with the useof the bacterial bioluminescence in behavior of the host. Thissymbiosis is discussed in light of other cyclically transmittedanimal-bacterial associations.     

Comparative morphology of the carpel in the Liliaceae: Baeometra, Burchardia and Walleria

The pistils in Baeometra, Burchardia and Walleria ate tricarpellate, and their ovules are mostly bitegmic. Baeometra has free styles and deep septal invaginations between the carpels. Its pistil is innervated by three dorsal bundles, three compound septal bundles (each of which may divide into two simple septal bundles above), six placental bundles, and six adjoining auxiliary placental bundles. The pistil of Burchardia resembles that of Baeometra , except that there are six simple septal bundles throughout and no auxiliary placental bundles. In Walleria the wings of adjoining carpels are completely fused (except for rare septal glands); there is a single compound style; additional vascular tissue is present in the central axis of the pistil up to the lowermost ovules; the carpels are fused with the floral cup above the base of the locules; and raphide idioblasts are present. Walleria has six "ventral" bundles, each of which appears to be the fusion product of a placental bundle with a simple septal bundle. Tribal affinities of these genera are discussed.     

海水鱼类共附生细菌群落研究进展

与海水鱼类处于共生、共栖、寄生或附生关系的细菌群落,称之为海水鱼类共附生细菌群落。这类细菌群落生活在海水鱼体表(皮肤、鳃)以及体内(消化道和血液、肌肉、肝脏、肾脏等内部组织器官),它们彼此之间以及与宿主之间存在着极其密切的关系,并且对于宿主的健康生长具有重要作用。然而,由于目前对养殖系统中的微生物群落中的致病微生物缺乏有效控制措施,处于迅速发展中的养殖产业经受着相当严重的疾病问题。因而,生态健康养殖被提到议事日程上来,并且日益受到重视,其中微生物生态调控是极其重要的一个环节。由于目前相关的基础微生物生态学资料比较缺乏,尤其是在国内作为微生物生态的基本组成部分,与微生物病害发生有着直接关系的大多数海水养殖鱼类的共附生细菌群落研究资料相当缺乏。因此,很有必要开展海水养殖鱼类共附生细菌群落相关研究。在此背景下,从研究的目的和意义以及国内外研究现状包括宿主海水鱼类种类、共附生细菌群落类别、共附生细菌群落的影响因素、共附生细菌群落对宿主的作用等方面综述了海水鱼类共附生细菌群落的研究进展,并对此类研究趋势进行了展望,为开展相关研究提供一定的参考。