基诺族传统食用植物的民族植物学研究

基诺族是国务院１９７９年确认的我国第５６个民族,至今仍依赖于歇农业即刀耕火种为生,自给自足的自然经济是他们主要经济形式。除在轮歇地内栽培少数几种作物外,基诺族的菜肴绝大部分采自其周围的林地、山野。本文记述了基诺族的传统食用植物１７９种,其中野菜类８６种、野生水果类３７种,栽培植物５４种。     

Characterization of a Synechococcus sp. strain PCC 7002 mutant lacking Photosystem I. Protein assembly and energy distribution in the absence of the Photosystem I reaction center core complex

A Synechococcus sp. strain PCC 7002 psaAB::cat mutant has been constructed by deletional interposon mutagenesis of the psaA and psaB genes through selection and segregation under low-light conditions. This strain can grow photoheterotrophically with glycerol as carbon source with a doubling time of 25 h at low light intensity (10 E m^–2 s^–1). No Photosystem I (PS I)-associated chlorophyll fluorescence emission peak was detected in the psaAB::cat mutant. The chlorophyll content of the psaAB::cat mutant was approximately 20% that of the wild-type strain on a per cell basis. In the absence of the PsaA and PsaB proteins, several other PS I proteins do not accumulate to normal levels. Assembly of the peripheral PS I proteins PsaC,PsaD, PsaE, and PsaL is dependent on the presence of the PsaA and PsaB heterodimer core. The precursor form of PsaF may be inserted into the thylakoid membrane but is not processed to its mature form in the absence of PsaA and PsaB. The absence of PS I reaction centers has no apparent effect on Photosystem II (PS II) assembly and activity. Although the mutant exhibited somewhat greater fluorescence emission from phycocyanin, most of the light energy absorbed by phycobilisomes was efficiently transferred to the PS II reaction centers in the absence of the PS I. No light state transition could be detected in the psaAB::cat strain; in the absence of PS I, cells remain in state 1. Development of this relatively light-tolerant strain lacking PS I provides an important new tool for the genetic manipulation of PS I and further demonstrates the utility of Synechococcus sp. PCC 7002 for structural and functional analyses of the PS I reaction center.Abbreviations ATCC American type culture collection - Chl chlorophyll - DCMU 3-(3,4-dichlorophyl)-1,1-dimethylurea - DBMIB 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone - HEPES N-[2-hydroxyethyl]piperazine-N-[2-ethanesulfonic acid] - PCC Pasteur culture collection - PS I Photosystem I - PS II Photosystem II - SDS sodium dodecyl sulfate     

Sequence Features Surrounding the Translation Initiation Sites Assigned on the Genome Sequence of Synechocystis sp. Strain PCC6803 by Amino-terminal Protein Sequencing

To characterize the sequence features surrounding the translationinitiation sites on the genome of Synechocystis sp. strain 6803,the total proteins extracted from the cell were resolved bytwo-dimensional electrophoresis, and the amino-terminal sequencesof the relatively abundant protein spots were determined. Bycomparison of the determined amino-terminal sequences with thenucleotide sequence of the entire genome, the translation initiationsites of a total of 72 proteins were successfully assigned onthe genome. The sequence features emerged from the nucleotidesequences at and surrounding the translation initiation siteswere as follows: (1) In addition to the three initiation codons,ATG, GTG, and TTG, evidence was obtained that ATT was also usedas a rare initiation codon; (2) the core sequences (GAGG, GGAGand AGGA) of the Shine-Dalgarno sequence were identified inthe appropriate position preceding the 35 initiation sites (48.6%);and (3) the preferential sequence surrounding the initiationcodons was formulated as 5'-YY[· · ·]R-3'where Y and R denote pyrimidine and purine nucleotides, respectively,and three dots represent the initiation codons. The result obtainedwould provide valuable information for improvement of the gene-findingsoftware, and the approach used in this study should be applicablefor comprehensive analysis of the expression profiles of cellularproteins.     

Role of light and photosynthesis on the acclimation process of the cyanobacteriumSpirulina platensis to salinity stress

The response ofSpirulina platensis cells to salinity stress was studied. Once adapted to the higher osmoticum, photosynthetic parameters such as the maximum rate of photosynthesis under saturating irradiance (P_max) and the initial slope of the P-I curve () are reduced by 15% and 25% in 0.5 M NaCl grown cells, respectively. Salt-adapted cells have a modified biochemical composition; reduced protein and chlorophyll content, and an increased level of carbohydrates. The reduction in the photosynthetic capacity of the salt-adaptedSpirulina cells reflects a lower ability to utilize light energy and results in an increase in the susceptibility of the stressed cells to photoinhibition. This conclusion is supported by the finding that cultures exposed to salt stress show not only a decrease in growth rate (), but lose the ability to respond to increased irradiance with an increase in growth. The use of variable fluorescence as a fast and reliable measurement to follow the changes in PSII of salt-stressesSpirulina cells enables following the early events of salinity shock. It indicates that as soon as the cells are exposed to salt, a protection mechanism is induced. This mechanism does not require any protein synthesis and may take place even in the dark, though at somewhat reduced effectiveness. The significance of the result in providing a better understanding of the interaction between two environmental stresses — light and salinity — and their application in the outdoor mass cultivation ofSpirulina are discussed.Author for correspondence     

蓝藻的类金属硫蛋白及其研究进展

单细胞蓝藻中的类金属硫蛋白已经得到分离纯化,并在蛋白质水平上与标准的哺乳动物金属硫蛋白做了对比性分析,发现二者氨基酸组成和序列差异很大,前者只形成一个结构域,但二级结构和金属结合性质具有一定的相似性,是进化上功能趋同的表现．同时克隆并分析了它的基因ORF结构,研究了金属诱导和逆向转录抑制对于蛋白质表达的调控及类似于哺乳动物金属硫蛋白基因具有的放大和重排现象机理,提出了近期研究的重点和方向．     

Trace metals in edible marine molluscs and crustaceans from Lebanon

Samples of the edible tissue of cephalopod molluscs (cuttlefish, squid, octopus) and crustaceans (lobster, shrimp) collected off the coast of Lebanon were found to concentrate similar levels of cadmium, copper, nickel, and chromium. Lead and zinc were highest in the cephalopods and iron was highest in the crustaceans.The molluscs collected from Beirut had higher levels of many metals than those taken from the other locations. The Beirut octopus had higher lead, cadmium, copper, iron, and chromium. Lead, cadmium, and copper were also highest in the Beirut cuttlefish while iron and zinc were elevated. The crustaceans from Beirut showed no strong tendency to concentrate higher metal levels, except for the Beirut lobster which had higher copper than the other samples.In the cuttlefish, the analysis of bone showed generally higher cadmium, zinc, nickel, and chromium but lower copper and iron than the muscle. However, at Beirut, the bone samples had much higher iron. Levels of most metals in the exoskeletons of the lobster and shrimp were quite similar to those in the muscle tissue with the exception of iron in the lobster which was highest in the exoskeleton, and zinc in both crustaceans, which was more highly concentrated in the muscle.     

δ-Aminolaevulinate biosynthesis in the cyanobacterium Synechococcus 6301

The cyanobacterium (blue-green alga) Synechococcus 6301 incorporated a large amount of isotope from [1-¹⁴C] and [2-¹⁴C]acetate into phaeophorbide a obtained from chlorophyll a and into glutamatein cell protein; very little radioactivity was present in aspartate in cell protein. This distribution of isotope indicates that aspartate and the tetrapyrrole of chlorophyll a are not derived from a common C₄, precursor. The ratios of the specific radioactivities of phaeophorbide a to glutamate for organisms grown in the presence of 1-¹⁴C] and [2-⁴C ] acetate were 2.5:1 and 10:1 respectively. These are close to the theoretical values for the C₅, route to δ-aminolaevulinate which indicates that this is the only pathway to the tetrapyrrole precursor in Synechococcus 6301.     

Ecology of a marineRivularia population

An account is given of the environmental chemistry and physiological ecology of a population ofRivularia atra growing in the upper eulittoral of Tyne Sands, a sheltered bay in S-E. Scotland. Large masses of detached seaweed tend to be deposited in the supralittoral of this bay and their decay leads to elevated levels of dissolved phosphate (typically 50–150 μg 1⁻¹ P) in the water of shallow pools of the upper eulittoral. Much (usually 50%) of this phosphate is organic, as opposed to phosphate in the open sea just outside the bay, where it is almost entirely inorganic. This organic phosphate is presumably available to theRivularia, as colonies show marked alkaline phosphatase activity. The colonies are small (mostly <1 mm diameter), but with a high nitrogenase activity (expressed per unit chlorophyll) in the light are high (sometimes approaching 0.2 nM C₂H₄ μg chl a⁻¹ min⁻¹ × 10⁻³) but there is a rapid and very marked drop on transfer to the dark. It is suggested that this latter feature may be of adaptive significance for this population, as colonies in many pools are covered intermittently by sand.     

Mass cultivation of the nitrogen-fixing cyanobacteriumGloeotrichia natans,indigenous to rice-fields

Gloeotrichia natans, a nitrogen fixing cyanobacterium common in rice fields in the Philippines, was used for studies to establish key features of its physiology and potential production in outdoor cultures. Under optimal growth conditions (38 °C, pH 8.0, no carbon enrichment) the specific growth rate of rice-field isolate was 0.076 h^–1. The pH of the medium (between 6.5 and 9.0) did not influence the growth rate, but it did affect phycobiliprotein content, as reflected by a change in colour. At pH 7.0 the culture was green-brown, with phycobiliproteins constituting up to 10% of the total protein, while at pH 9.0 the culture was brownish-black and the pigment content was as high as 28% of the total protein. In outdoor cultures the specific growth rate was related directly to cell density in the range of 0.7–1.5 g dry weight 1^–1 at a rate of stirring of 30 rpm, and inversely related to cell density at half this rate. At a stirring of 30 rpm, daily production of outdoor cultures harvested to maintain cell densities of 0.7, 1.15 andw 1.5 g 1^–1 were 14.7, 17.1 and 18.1 g m^–2 d^t, respectively. This rate of production was maintained for more than 45 days. Phycobiliprotein content in the culture kept at a density of 1.5 g 1^–1 reached 14% of the total biomass.