The time dependence of bacterial spore germination.

The absorbance of a suspension of germinating bacterial spores describes a sigmoidal time dependence. This behavior is accurately described by a model which considers that the spore must pass through an intermediate state before reaching its final, germinated state. By attributing to each of these three states a characteristic turbidity coefficient, it is possible to write an expression for the absorbance of the suspension at any time after initiation of germination. The transition between neighboring states is characterized by a probability coefficient which is a function of the experimental variables, but which is independent of time. It is thus possible to separate the underlying time dependence of germination itself, characterized by the changes of state, from the observed manifestation of this phenomenon.     

An autocatalytic model for bacterial spore germination.

The sigmoidal response observed in kinetic studies of germinating bacterial spores, using nephelometric techniques and phase contrast microscope photometry, is analysed by postulating an autocatalytic process. A scheme A to B to C, where B catalyses the degradation of A, is applied to describe the response accurately by three rate constants. The autocatalytic model is compared with previous proposals for quantifying germination studies and for interpreting the effect of different experimental conditions on initiation of germination. Its effectiveness is demonstrated by quantifying published results for a germinating single spore determined by phase contrast microscopy, and nephelometric results for spore suspensions, including the effect of temperature on the rate of initiation of germination. Although developed for quantitative analysis of spore germination, the model is applicable to other autocatalytic phenomena. To assist the experimentalist, a simple accurate method for deriving the three constants specifying the sigmoidal characteristic is described.     

Inhibition of microsporidian spore germination

Microsporidia are obligate intracellular parasites that are increasingly recognized as significant causes of disease in AIDS patients. Gordon Leitch, Govinda Visvesvara and Qing He here describe the deployment of the microsporidian spore infection apparatus, the polar filament, and show how this may be a useful site for chemotherapeutic interdiction of the infections caused by these parasites.     

蕨类植物孢子萌发影响因素的研究进展

蕨类植物经孢子萌发 ,产生配子体和形成孢子体 ,从而完成其世代交替的生活史 ;其中孢子萌发在整个生活周期中起着关键性的作用。简要介绍了近年来关于孢子萌发的研究进展。     

Photocontrol of fungal spore germination

Germination of Puccinia graminis f. sp. tritici uredospores is inhibited by continuous irradiation. Prehydration of spores enhances both dark germination and photoinhibition. Simultaneous irradiation with ineffective red (653 nanometers) and inhibitory far red light (720 nanometers) results in partial nullification of the inhibition brought about by far red light alone. This result would be consistent with the involveent of a photoreversible pigment system similar to phytochrome, operating via the high irradiance reaction.     

Initiation of bacterial spore germination

To investigate the problem of initiation in bacterial spore germination, we isolated, from extracts of dormant spores of Bacillus cereus strain T and B. licheniformis, a protein that initiated spore germination when added to a suspension of heat-activated spores. The optimal conditions for initiatory activity of this protein (the initiator) were 30 C in 0.01 to 0.04 m NaCl and 0.01 m tris(hydroxymethyl)aminomethane (pH 8.5). The initiator was inhibited by phosphate but required two co-factors, l-alanine (1/7 of K(m) for l-alanine-inhibited germination) and nicotinamide adenine dinucleotide (1.25 x 10(-4)m). In the crude extract, the initiator activity was increased 3.5-fold by heating the extract at 65 C for 10 min, but the partially purified initiator preparation was completely heat-sensitive (65 C for 5 min). Heat stability could be conferred on the purified initiator by adding 10(-3)m dipicolinic acid. A fractionation of this protein that excluded l-alanine dehydrogenase and adenosine deaminase from the initiator activity was developed. The molecular weight of the initiator was estimated as 7 x 10(4). The kinetics of germination in the presence of initiator were examined at various concentrations of l-alanine and nicotinamide adenine dinucleotide.     

Streptomyces viridochromogenes spore germination initiated by calcium ions.

Initiation of germination of heat-activated Streptomyces viridochromogenes spore occurs in media containing only calcium ions and organic buffer. The calcium-induced initiation of germination was accompanied by a decrease in absorbance of the spore suspension, an increased rate of endogenous metabolism, the loss of spore carbon, and the loss of heat resistance. Calcium amounts to 0.28% of the dry weight of freshly harvested spores. The amount of calcium remained the same after incubation of spores in water after heat activation. The spore content of calcium doubled after incubation in 0.5 mM CaCl2 for 5 min at 4 degrees C and during calcium-induced germination. Nearly all of the calcim appears to be bound to sites external to the spore membrane, since the chelating agents (ethylenedinitrilo) tetraacetic acid and arsenazo III removed virtually all of the calcium ions. The calcium ions must be present during the entire initiation of germination period. Germination ceases after an (ethylenedinitrilo) tetraacetic acid wash and begins again immediately after addition of calcium ions.     

RNA synthesis during spore germination in Bacillus subtilis.

Summary We have analyzed the RNA synthesized during spore germination in Bacillus subtilis. Early in germination there is little incorporation of [³H]uridine into RNA. A large increase in incorporation into RNA was found at 45–60 min into germination which was in part due to increases in the specific activity of the UTP pool. When corrected for specific activity changes, the instantaneous rate of RNA synthesis showed a seven to tenfold increase between 30 and 45 min of germination. Polyacrylamide gel electrophoresis studies showed that the RNA synthesized during germination appeared very similar to the RNA made during vegetative growth. DNA-RNA hybridization studies indicated that mRNA and rRNA were synthesized throughout germination. Their relative proportions remained constant and were very similar to the composition of RNA synthesized during vegetative growth.In partial fulfillment of the requirements for the doctoral degree by A.S. in the Department of Microbiology at the New York University School of Medicine     

L-Proline site for triggering Bacillus megaterium spore germination.

Germination of $\text{Bacillus megaterium}$ QM B1551 spores can be triggered by L-proline chloromethyl ketone at ～ 10 fold lower concentrations than L-proline. [³H] L-proline chloromethyl ketone bound to several protein fractions, one of which was decreased in a mutant (JV137) that cannot be triggered by L-proline. Treatment of spores with [³H] acetic anhydride specifically inhibited L-proline triggered germination, and also covalently modified the same protein fraction which appears to be bound to the spore membrane. These results indicate that it is possible to identify a protein fraction in spores that may play a key role in triggering spore germination.     

Mutants of Dictyostelium discoideum defective in spore germination.

After activation, wild-type Dictyostelium discoideum spores germinate rapidly and synchronously in phosphate buffer as well as in complex medium. Mutants defective in spore germination were isolated and characterized. These mutants (called grm) did not germinate normally in buffer but did germinate in complex medium in the presence of bacteria. One mutant (grm B) swelled normally, but amoebae were not formed. Another mutant (grm F) swelled and germinated poorly in buffer. The members of the third group of mutants (A, C, D, and E) did not swell or give rise to amoebae in buffer.     

环境因子对蕨类植物孢子萌发的影响

蕨类植物通过孢子萌发形成独立生活的配子体,配子体能够形成精子器和颈卵器,进而通过受精作用形成新的孢子体。孢子萌发是蕨类植物生活史过程中配子体世代向孢子体世代转变的关键步骤。同时,此过程不仅受到多种环境因子的影响,也是研究细胞核极性移动、细胞不对称分裂、假根极性生长等独特的细胞学事件的良好模型。迄今为止,人们已经研究发现多种环境因子对约200余种蕨类植物孢子萌发有影响。总结了环境因子对蕨类植物孢子萌发影响的规律如下:(1)孢子萌发除了受到光照强度影响外,主要受光质的影响,光质的影响主要表现为4种方式:①孢子萌发受红光刺激与远红光抑制像开关一样调控;②孢子萌发不受远红光抑制;③孢子萌发受蓝光抑制;④孢子只能在黑暗条件下萌发。(2)重力作用会影响孢子细胞核移动,进而影响孢子细胞发育的极性。(3)赤霉素(GA)能增加孢子萌发率或帮助孢子打破休眠。成精子囊素与GA作用相似,启动或促进孢子萌发。而脱落酸(ABA)、茉莉酸(JA)和乙烯等其它激素对孢子萌发的影响相对较小。(4)不同植物孢子有着各自最适的萌发培养基条件,如不同种类孢子对MS培养基中无机盐含量、蔗糖含量、pH值的要求不同。孢子外被中的Ca2+、Mn2+和Mg2+,培养基中的Cd2+和La3+,以及孢子接种密度、萌发空间CO2含量也会对孢子萌发造成影响。(5)多数蕨类植物孢子在15-30℃可以萌发,最适萌发温度为25℃。(6)4℃和液氮储藏可以延长孢子寿命并保持较高萌发率。     

Influence of certain environmental factors on spore germination and spore differentiation inPithophora oedogonia

Of the light- and dark-stored spores ofPithophora oedogonia for over a period of one and half years, the latter exhibited complete failure of germination under controlled culture conditions. pH 8, blue light and 1 klx intensity of white light proved to be ideal conditions as they resulted in optimum germination of akinetes. pH 5, green light and 0.25 klx light intensity delayed the initiation of sporulation and also reduced percentage sporulation. All filaments died before sporulation in pH 4.     

Bacterial spore germination and protein mobility

Fluorescence recovery after photobleaching (FRAP) of green fluorescent protein (GFP) has been used to report on protein mobility in single spores. Proteins found in dormant Bacillus spores are not mobile; however, mobility is restored when germination occurs and the core rehydrates. Spores of a cwlD mutant, in which the cortex is resistant to hydrolysis, are able to complete the earliest stages of germination in response to a specific germinant stimulus; in these circumstances, the protein in the spore remains immobile. Therefore, the earliest stages of spore germination, including loss of resistance to extreme heat and the complete release of the spore component dipicolinic acid, are achieved without the restoration of protein mobility.     

Biochemistry of spore germination in Phycomyces

Abstract The constitutionally dormant spores of Phycomyces blakesleeanus can be activated by heat shock or treatment with several monocarboxylic acids. Activation is followed first by a general stimulation of metabolism, e.g. respiration, protein-, RNA- and cell-wall synthesis, and subsequently by nuclear division and germ-tube emergence. Initial germination is not dependent on RNA synthesis and can even start without protein synthesis. The first common effect of different activating treatments is a transient rise in cyclic AMP (cAMP) content, caused by a change in phosphodiesterase activity after heat activation, and by unknown factors during activation by acids. cAMP transiently activates trehalase and glycerol-3-phosphatase in the spores. The activation of these enzymes causes a quick turnover of trehalose into glycerol. During the same period, the water status of the cells is altered so dramatically that perhaps this may explain at least part of the stimulation of metabolism in the germinating spore.