Protozoal digestion of coat-defective Bacillus subtilis spores produces "rinds" composed of insoluble coat protein

The Bacillus subtilis spore coat is a multilayer, proteinaceous structure that consists of more than 50 proteins. Located on the surface of the spore, the coat provides resistance to potentially toxic molecules as well as to predation by the protozoan Tetrahymena thermophila. When coat-defective spores are fed to Tetrahymena, the spores are readily digested. However, a residue termed a "rind" that looks like coat material remains. As observed with a phase-contrast microscope, the rinds are spherical or hemispherical structures that appear to be devoid of internal contents. Atomic force microscopy and chemical analyses showed that (i) the rinds are composed of insoluble protein largely derived from both outer and inner spore coat layers, (ii) the amorphous layer of the outer coat is largely responsible for providing spore resistance to protozoal digestion, and (iii) the rinds and intact spores do not contain significant levels of silicon.     

Genetically controlled removal of "spore photoproduct" from deoxyribonucleic acid of ultraviolet-irradiated Bacillus subtilis spores

Previous genetic analysis indicated that at least two genes determine the ultraviolet (UV) sensitivity of Bacillus subtilis spores. The present study shows that these genes independently control two distinguishable processes for removing UV-induced spore photoproduct (5-thyminyl-5,6-dihydrothymine, or TDHT) from spore deoxyribonucleic acid. The first, is a spore repair mechanism by which TDHT is removed rapidly without appearing in acid-soluble form. This mechanism, which is demonstrated in both UV-resistant and excision-deficient strains, operates to a certain extent during germination without requiring vegetative growth. The second, demonstrated in a mutant which lacks the first mechanism, removes TDHT relatively slowly and only if germinated spores are allowed to develop toward vegetative cells. The latter mechanism appears identical to excision-resynthesis repair, since the mutation abolishing it renders the irradiated vegetative cells incapable of removing cyclobutane-type pyrimidine dimers. Blocking either one of these mechanisms only slightly affects the UV sensitivity of spores, but blocking both prevents TDHT removal and gives high UV sensitivity.     

"Spore plate method" for transformation of steroids by fungal spores entrapped in silica gel g

A new technique for investigating steroid biotransformations involving the use of glucose-treated Silica Gel G thin-layer chromatography plates spotted with fungal spores and steroid substrates is described. The conversion is followed by the detection and identification of steroid metabolites and is carried out on single plates by using the spores of different fungi. During the entire process, the spores remain on the original spots and microscopical examination revealed no germination. The method was successfully applied to as little as 30 μg of substrates, and a single plate could be used to detect the steroid metabolizing activity of spores of as many as 15 different cultures.     

Dual effects of single-walled carbon nanotubes coupled with near-infrared radiation on <Emphasis Type="Italic">Bacillus anthracis</Emphasis> spores: inactivates spores and stimulates the germination of surviving spores

Background

Bacillus anthracis is a pathogen that causes life-threatening disease--anthrax. B. anthracis spores are highly resistant to extreme temperatures and harsh chemicals. Inactivation of B. anthracis spores is important to ensure the environmental safety and public health. The 2001 bioterrorism attack involving anthrax spores has brought acute public attention and triggered extensive research on inactivation of B. anthracis spores. Single-walled carbon nanotubes (SWCNTs) as a class of emerging nanomaterial have been reported as a strong antimicrobial agent. In addition, continuous near infrared (NIR) radiation on SWCNTs induces excessive local heating which can enhance SWCNTs’ antimicrobial effect. In this study, we investigated the effects of SWCNTs coupled with NIR treatment on Bacillus anthracis spores.

Results and discussion

The results showed that the treatment of 10 μg/mL SWCNTs coupled with 20 min NIR significantly improved the antimicrobial effect by doubling the percentage of viable spore number reduction compared with SWCNTs alone treatment (88% vs. 42%). At the same time, SWCNTs-NIR treatment activated the germination of surviving spores and their dipicolinic acid (DPA) release during germination. The results suggested the dual effect of SWCNTs-NIR treatment on B. anthracis spores: enhanced the sporicidal effect and stimulated the germination of surviving spores. Molecular level examination showed that SWCNTs-NIR increased the expression levels (>2-fold) in 3 out of 6 germination related genes tested in this study, which was correlated to the activated germination and DPA release. SWCNTs-NIR treatment either induced or inhibited the expression of 3 regulatory genes detected in this study. When the NIR treatment time was 5 or 25 min, there were 3 out of 7 virulence related genes that showed significant decrease on expression levels (>2 fold decrease).

Conclusions

The results of this study demonstrated the dual effect of SWCNTs-NIR treatment on B. anthracis spores, which enhanced the sporicidal effect and stimulated the germination of surviving spores. SWCNTs-NIR treatment also altered the expression of germination, regulatory, and virulence-related genes in B. anthracis.

     

Uninucleate spores of Phycomyces

Summary Under most culture conditions only 0.3% of the vegetative spores of Phycomyces blakesleeanus are uninucleate. On an acidified minimal medium, the uninucleate fraction can be raised up to 4.5% of the spores. The spore population can be fractionated in a gradient under gravity (1xg) yielding fractions that contain over 80% uninucleate spores. These uninucleate spores are fully viable. When the spores to be fractionated are obtained from a heterokaryotic mycelium, the uninucleate fraction produces homokaryotic mycelia.     

Fusarium andDidymella-neglected spores in the air

Summary This paper reports about the occurence ofFusarium- andDidymella spores in the air of Essen/FRG. During the spore season 1990, the spore concentration was measured on several days with a volumetric pollen trap by hourly analysis. The calculated amount of spores per hour is compared to the data of a pluviometer and the values of the relative humidity during the same period.The occurence of both spore types in the air and high relative humidity (>80%) are correlated in a highly significant way (P<0.001). The dispersion of spores starts when rain begins or directly after the precipitation.Didymella reaches higher concentrations thanFusarium in the air (Maximum values:Didymella 30000 spores/m³,Fusarium only 800 spores/m³). During the emission of the spores the temperature varied between 10°C und 20°C degrees. Didymella andFusarium must be an important allergenic source in the outdoor area, because of their allergen-loaded biological aerosols. The question of providing well defined extracts ofDidymella exitialis is given to the pharmaceutical industry.     

The source of the heat resistance of bacterial spores: Study of water in spores by NMR

It has been postulated that the heat stabilization of the essential macromolecules in the core of the spore may be produced by dehydration at two levels: (i) the spore is drier at high relative humidity than the vegetative cell and (ii) the core of the spore may be less hydrated than the cortex and the coat. The latter postulate was subjected to experimental testing by ¹H-NMR studies of the water signal in the five species of spores and coat and (coat + cortex) preparations. The transverse relaxation rate $\text{(}\text{1}\text{T}{}_2\text{)}$ was determined in samples equilibrated at constant relative humidity. To allow for the effect of paramagnetic ions on $\text{1}\text{T}{}_2$ a model system (wool keratin) was studied in the presence of known amounts of Ca(II), Mn(II), Cu(II), Ni(II) and Fe(III). Because of the dominant effect of Mn(II) on $\text{1}\text{T}{}_2$, the effect of small amounts of other metal ions in spores was neglected. The relaxation rate of water at a particular relative humidity and manganese concentration was consistently less for intact spores than for coat or coat + cortex, hence the water in the core is more mobile than in the outer integuments. Sorption isotherm studies have shown that at a particular relative humidity there is about as much water in the core as in the cortex and coat. These two results taken together indicate that the hypothesis that the core is drier than the cortex and coat is incorrect, hence the spore is not heat-stabilized in this way. A theory is proposed in which heat stabilization is attributed to immobilization of essential enzymes and nuclei acids by a solid support, calcium dipicolinate, in a similar fashion to the heat stabilization of enzymes in a charged polymer matrix. It is proposed that stabilization is effected by electrostatic and hydrogen bonds between the calcium dipicolinate and the essential macromolecules. Experiments in progress show that enzymes and DNA are heat-stabilized in vitro by calcium dipicolinate.