Effect of soluble solids concentration on Neosartorya fischeri inactivation using UV-C light.

Ascospores of Neosartorya fischeri are heat-resistant and can survive thermal commercial treatments normally applied to the juices, as apple juice. Non-thermal processing of food such as exposure to ultraviolet light (UV-C) is reported to induce minimal quality changes while reduces microbial load. The main objective of this study was to determine the effect at different soluble solids concentration (12, 25, 30, 40, 50, 60 and 70 °Brix) on N. fischeri ascospores inactivation in apple juice, using UV-C light intensity (38 W/m2). Weibull model was fitted to experimental data. Then, a secondary model was used to describe how the inactivation kinetic parameters varied with the changes in soluble solids concentration. Results showed that the UV-C light had influence on N. fischeri ascospores inactivation in apple juice even at the highest soluble solids concentrations used, reaching approximately 4 log reductions at all concentrations used. The inactivation parameters, obtained by Weibull model, were δ (dose for the first decimal reduction) and p (the shape factor). Exponential model was chosen to describe the influence of soluble solids concentration on δ and p parameters. It can be concluded that UV-C light is a promising treatment with a drastic impact on the loads of N. fischeri, especially when low soluble solids concentration is used and a model was obtained to describe Brix effect.

Effectiveness of an ultraviolet-C disinfection system for reduction of healthcare-associated pathogens.

BACKGROUND: Healthcare-associated infections caused by multidrug-resistant (MDR) pathogens are significantly associated with increased mortality and morbidity. Environmental cleaning can reduce transmission of these pathogens but is often inadequate. Adjunctive methods are warranted to enhance the effectiveness of disinfection particularly in hospital settings where healthcare-associated infections are of major concern. METHODS: We conducted a study to examine the effectiveness of a mobile, automatic device, Hyper Light Disinfection Robot (model: Hyper Light P3), which utilized ultraviolet-C (UV-C) to kill MDR-Pseudomonas aeruginosa, MDR- Acinetobacter baumannii, methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus faecium (VRE), Mycobacterium abscessus and Aspergillus fumigatus. The performance of this device in disinfecting hospital rooms previously admitted by patients harboring MRSA and VRE was also assessed. RESULTS: Except for VRE and M. abscessus, more than 3 log10 reduction of vegetative bacteria colonies was observed after UV-C irradiation of 5 min at a distance of 3 m from the device. At the distance of 1 m, substantial and comparable reduction of colonies was observed across all tested microorganisms regardless of exposure time. The killing effect was less pronounced for A. fumigatus particularly at the distance of 2-3 m. In uncleaned hospital rooms, there was significant reduction in the number of bacteria colonies sampled from different surfaces after UV-C irradiation for 15 min. CONCLUSIONS: UV-C disinfection system was effective in killing MDR pathogens. Further study is warranted to confirm its effectiveness as an adjunctive method in disinfecting hospital environment.

Gamma radiation-induced in vitro hormetic apogamy in the fern Pityrogramma calomelanos (L.) link.

Pityrogramma calomelanos (L.) Link, popularly known as "Silver fern" has significant importance as a medicinal plant used traditionally for its astringent, analgesic, anti-haemorrhagic, anti-hypertensive, anti-pyretic and anthelminthic properties. This fern demonstrates an increased morphogenetic potential towards sporophyte formation, upon exposure to low doses of gamma radiation. Young sporophytic leaf crosier cultures were established in vitro on agar based Knop's media with and without 20 g/l sucrose. The cultures were subjected to 60Co radiations in the range of 2.5-100 Gy. Apospory (production of gametophytes on sporophytic tissue without spores) was observed on leaf tissue cultured on Knops media with and without sucrose in P. calomelanos, at the end of 60 days. 5 Gy treated explants showed high number of aposporous gametophytes and was comparable to the control. Other tested doses reduced the aposporous gametophyte production significantly. In the second phase of the experimentation, the cultures were retained on the gametophyte induction media for a period of 4 weeks. Aposporous gametophytes were observed to proliferate with occasional development of antheridia. At the end of 4 weeks, morphogenetic development on the gametophytic tissue resulted in a significantly higher number of apogamous sporophytes (production of sporophytes without fusion of gametes) were obtained on 5 Gy treated tissue as compared to control and all the other treated explants. Apogamous sporophytes thus produced were successfully grown in the greenhouse and transferred to the field. Thus the use of gamma radiation in vitro not only reduced the need for sucrose for induction of apospory in P.calomelanos, it also exhibited hormesis at 5 Gy for improved sporophyte production.

Spores potentially dispersed to longer distances are more tolerant to ultraviolet radiation: A case study in the moss genus Orthotrichum.

PREMISE OF THE STUDY: Ultraviolet (UV) radiation influences the viability of algal spores and seed-plant pollen depending on the species, the dose, and the wavelength. In bryophytes, one of the dominant groups of plants in many habitats, UV radiation could determine their spore dispersal strategy, and such data are critical for reconstructing the ancestral state in plants and for determining the distribution range and persistence of bryophyte species. METHODS: Spores of four bryophyte species of the moss genus Orthotrichum that were either hygrochastic or xerochastic (spores dispersed under wet or dry conditions, respectively) were exposed to realistic doses of UV radiation under laboratory conditions. Spore viability was evaluated through germination experiments and, for the first time in bryophytes, ultrastructural observations. Given that the UV-B doses used were relatively higher than the UV-A doses, the UV effect was probably due more to UV-B than UV-A wavelengths. KEY RESULTS: All four species reduced their spore germination capacity in a UV dose-dependent manner, concomitantly increasing spore ultrastructural damage (cytoplasmic and plastid alterations). Most spores eventually died when exposed to the highest UV dose. Interestingly, spores of hygrochastic species were much more UV-sensitive than those of xerochastic species. CONCLUSIONS: UV tolerance determines moss spore viability, as indicated by germination capacity and ultrastructural damage, and differs between spores of species with different dispersal strategies. Specifically, the higher UV tolerance of xerochastic spores may enable them to be dispersed to longer distances than hygrochastic spores, thus extending more efficiently the distribution range of the corresponding species.

A Plant Cryptochrome Controls Key Features of the Chlamydomonas Circadian Clock and Its Life Cycle.

Cryptochromes are flavin-binding proteins that act as blue light receptors in bacteria, fungi, plants, and insects and are components of the circadian oscillator in mammals. Animal and plant cryptochromes are evolutionarily divergent, although the unicellular alga Chlamydomonas reinhardtii (Chlamydomonas throughout) has both an animal-like cryptochrome and a plant cryptochrome (pCRY; formerly designated CPH1). Here, we show that the pCRY protein accumulates at night as part of a complex. Functional characterization of pCRY was performed based on an insertional mutant that expresses only 11% of the wild-type pCRY level. The pcry mutant is defective for central properties of the circadian clock. In the mutant, the period is lengthened significantly, ultimately resulting in arrhythmicity, while blue light-based phase shifts show large deviations from what is observed in wild-type cells. We also show that pCRY is involved in gametogenesis in Chlamydomonas pCRY is down-regulated in pregametes and gametes, and in the pcry mutant, there is altered transcript accumulation under blue light of the strictly light-dependent, gamete-specific gene GAS28 pCRY acts as a negative regulator for the induction of mating ability in the light and for the loss of mating ability in the dark. Moreover, pCRY is necessary for light-dependent germination, during which the zygote undergoes meiosis that gives rise to four vegetative cells. In sum, our data demonstrate that pCRY is a key blue light receptor in Chlamydomonas that is involved in both circadian timing and life cycle progression.

The decision to germinate is regulated by divergent molecular networks in spores and seeds.

Dispersal is a key step in land plant life cycles, usually via formation of spores or seeds. Regulation of spore- or seed-germination allows control over the timing of transition from one generation to the next, enabling plant dispersal. A combination of environmental and genetic factors determines when seed germination occurs. Endogenous hormones mediate this decision in response to the environment. Less is known about how spore germination is controlled in earlier-evolving nonseed plants. Here, we present an in-depth analysis of the environmental and hormonal regulation of spore germination in the model bryophyte Physcomitrella patens (Aphanoregma patens). Our data suggest that the environmental signals regulating germination are conserved, but also that downstream hormone integration pathways mediating these responses in seeds were acquired after the evolution of the bryophyte lineage. Moreover, the role of abscisic acid and diterpenes (gibberellins) in germination assumed much greater importance as land plant evolution progressed. We conclude that the endogenous hormone signalling networks mediating germination in response to the environment may have evolved independently in spores and seeds. This paves the way for future research about how the mechanisms of plant dispersal on land evolved.

Drinking water treatment with ultraviolet light for travelers -- Evaluation of a mobile lightweight system.

BACKGROUND: The SteriPEN(®) is a handheld device for disinfecting water with ultraviolet (UV) radiation. The manufacturer claims a reduction of at least 99.9% of bacteria, viruses, and protozoa. The present study intends to verify the general effectiveness of the device. Furthermore, the influence of bottle geometry and water movement is examined and the issue of user safety with regard to UV-C radiation is addressed. METHODS: The device was applied on water containing a known number of microorganisms (Escherichia coli, Staphylococcus aureus, and the spore of Geobacillusstearothermophilus) and the survival rate was examined. Three different types of bottles commonly used among travelers served as test containers. All tests were conducted with and without agitating the water during irradiation. Furthermore, a spectral analysis was performed on the light of the device. RESULTS: The SteriPEN(®) reached a mean reduction of more than 99.99% of bacteria and 99.57% of the spores when applied correctly. However, the results of the trials without agitating the water only yielded a 94.98% germ reduction. The device's maximal radiation intensity lies at 254 nm which is the wavelength most efficient in inactivating bacteria. The UV-C fraction is filtered out completely by common bottle materials. However, when applied in larger containers a portion of the UV-C rays exits the water surface. CONCLUSIONS: If applied according to the instructions the device manages a satisfactory inactivation of bacteria. However, it bears the danger of user errors relevant to health. Therefore, education on the risks of incorrect application should be included in the travel medical consultation. Also there are still aspects that need to be subject to further independent research.

Spectroscopy and viability of Bacillus subtilis spores after ultraviolet irradiation: implications for the detection of potential bacterial life on Europa.

One of the most habitable environments in the Solar System outside of Earth may exist underneath the ice on Europa. In the near future, our best chance to look for chemical signatures of a habitable environment (or life itself) will likely be at the inhospitable icy surface. Therefore, it is important to understand the ability of organic signatures of life and life itself to persist under simulated europan surface conditions. Toward that end, this work examined the UV photolysis of Bacillus subtilis spores and their chemical marker dipicolinic acid (DPA) at temperatures and pressures relevant to Europa. In addition, inactivation curves for the spores at 100 K, 100 K covered in one micron of ice, and 298 K were measured to determine the probability for spore survival at the surface. Fourier transform infrared spectra of irradiated DPA showed a loss of carboxyl groups to CO2 as expected but unexpectedly showed significant opening of the heterocyclic ring, even for wavelengths>200 nm. Both DPA and B. subtilis spores showed identical unknown spectral bands of photoproducts after irradiation, further highlighting the importance of DPA in the photochemistry of spores. Spore survival was enhanced at 100 K by ∼5× relative to 298 K, but 99.9% of spores were still inactivated after the equivalent of ∼25 h of exposure on the europan surface.

Light inhibits spore germination through phytochrome in Aspergillus nidulans.

Aspergillus nidulans responds to light in several aspects. The balance between sexual and asexual development as well as the amount of secondary metabolites produced is controlled by light. Here, we show that germination is largely delayed by blue (450 nm), red (700 nm), and far-red light (740 nm). The largest effect was observed with far-red light. Whereas 60 % of the conidia produced a germ tube after 20 h in the dark, less than 5 % of the conidia germinated under far-red light conditions. Because swelling of conidia was not affected, light appears to act at the stage of germ-tube formation. In the absence of nutrients, far-red light even inhibited swelling of conidia, whereas in the dark, conidia did swell and germinated after prolonged incubation. The blue-light signaling components, LreA (WC-1) and LreB (WC-2), and also the cryptochrome/photolyase CryA were not required for germination inhibition. However, in the phytochrome mutant, ∆fphA, the germination delay was released, but germination was delayed in the dark in comparison to wild type. This suggests a novel function of phytochrome as far-red light sensor and as activator of polarized growth in the dark.

Control of Bacillus licheniformis spores isolated from dairy materials in yogurt production.

To determine the effects of sporulation temperature and period on Bacillus licheniformis spore heat resistance, B. licheniformis strain No.25 spores were sporulated at 30, 37, 42, or 50°C for 11 d and at 50°C for 1.7, 4, 7, or 11 d. The heat resistance of B. licheniformis strain No.25 spores at 110°C increased with an increase in the sporulation temperature. Spores sporulated at 50°C were 1.4-fold more heat resistant than those sporulated at 30°C. Furthermore, the heat resistance of B. licheniformis strain No.25 spores at 110°C increased with an increase in the sporulation period. Spores sporulated for 11 d were 5.3-fold more heat resistant than those sporulated for 1.7 d. The heat resistance of B. licheniformis strain No.25 spores at 110°C increased with increases in the sporulation temperature and sporulation period. The results presented in this study can be applied to the pasteurization process to control B. licheniformis spores. Pasteurization at 110°C for about 60sec. is effective in controlling B. licheniformis spores isolated from dairy materials in yogurt production.

UVR defense mechanisms in eurytopic and invasive Gracilaria vermiculophylla (Gracilariales, Rhodophyta).

The invasive success of Gracilaria vermiculophylla has been attributed to its wide tolerance range to different abiotic factors, but its response to ultraviolet radiation (UVR) is yet to be investigated. In the laboratory, carpospores and vegetative thalli of an Atlantic population were exposed to different radiation treatments consisting of high PAR (photosynthetically active radiation) only (P), PAR+UV-A (PA) and PAR+UV-A+UV-B (PAB). Photosynthesis of carpospores was photoinhibited under different radiation treatments but photosystem II (PSII) function was restored after 12 h under dim white light. Growth of vegetative thalli was significantly higher under radiation supplemented with UVR. Decrease in chlorophyll a (Chl a) under daily continuous 16-h exposure to 300 µmol photons m(-2) s(-1) of PAR suggests preventive accumulation of excited chlorophyll molecules within the antennae to minimize the generation of dangerous reactive oxygen species. Moreover, an increase in total carotenoids and xanthophyll cycle pigments (i.e. violaxanthin, antheraxanthin and zeaxanthin) further suggests effective photoprotection under UVR. The presence of the ketocarotenoid ß-cryptoxanthin also indicates protection against UVR and oxidative stress. The initial concentration of total mycosporine-like amino acids (MAAs) in freshly-released spores increased approximately four times after 8-h laboratory radiation treatments. On the other hand, initial specific MAAs in vegetative thalli changed in composition after 7-day exposure to laboratory radiation conditions without affecting the total concentration. The above responses suggest that G. vermiculophylla have multiple UVR defense mechanisms to cope with the dynamic variation in light quantity and quality encountered in its habitat. Beside being eurytopic, the UVR photoprotective mechanisms likely contribute to the current invasive success of the species in shallow lagoons and estuaries exposed to high solar radiation.

Recruitment potential of a green alga Ulva flexuosa Wulfen dark preserved zoospore and its development.

The recruitment potential and the ability of Ulva flexuosa Wulfen zoospores to survive darkness were tested under different conditions in the present study. The dark preserved zoospore was cultured under a two-factor experimental design to test the effect of salinity and nitrate, effect of salinity and phosphate, effect of light and salinity, and effect of light and phosphate. The recruitment (germination and growth) of zoospores was significantly affected by light and salinity. The nitrate concentration of 20 µmol.l(-1) was found to initiate the process of germination and its subsequent growth and, its effect appeared greatest under 25 psu condition. While nitrate enhances the growth of biomass more than phosphate, both show a positive interactive effect on biomass increase when crossed with salinity. The combined effect of 25 psu salinity and 8 µmol.l(-1) phosphate exhibited higher biomass growth. There was a significant effect of light and salinity on the biomass of zoospore, though there was no significant interaction between the two factors. There was an increase in biomass of growing zoospores to increase in light intensity and 80 µmol.m(-2).s(-1) of light intensity was considered optimal. Similarly, high light intensity condition favored higher biomass growth and there was significant interaction between light (80 µmol. m(-2). s(-1)) and phosphate (4 µmol. l(-1)) in high salinity (35 psu) condition. The result of this study showed that dark preserved zoospores of U. flexuosa have the potential for recruitment and it gives us an understanding how different factors play a role in the process of recruitment.

Moist-heat resistance, spore aging, and superdormancy in Clostridium difficile.

Clostridium difficile spores can survive extended heating at 71°C (160°F), a minimum temperature commonly recommended for adequate cooking of meats. To determine the extent to which higher temperatures would be more effective at killing C. difficile, we quantified (D values) the effect of moist heat at 85°C (145°F, for 0 to 30 min) on C. difficile spores and compared it to the effects at 71 and 63°C. Fresh (1-week-old) and aged (≥20-week-old) C. difficile spores from food and food animals were tested in multiple experiments. Heating at 85°C markedly reduced spore recovery in all experiments (5 to 6 log(10) within 15 min of heating; P < 0.001), regardless of spore age. In ground beef, the inhibitory effect of 85°C was also reproducible (P < 0.001), but heating at 96°C reduced 6 log(10) within 1 to 2 min. Mechanistically, optical density and enumeration experiments indicated that 85°C inhibits cell division but not germination, but the inhibitory effect was reversible in some spores. Heating at 63°C reduced counts for fresh spores (1 log(10), 30 min; P < 0.04) but increased counts of 20-week-old spores by 30% (15 min; P < 0.02), indicating that sublethal heat treatment reactivates superdormant spores. Superdormancy is an increasingly recognized characteristic in Bacillus spp., and it is likely to occur in C. difficile as spores age. The potential for reactivation of (super)dormant spores with sublethal temperatures may be a food safety concern, but it also has potential diagnostic value. Ensuring that food is heated to >85°C would be a simple and important intervention to reduce the risk of inadvertent ingestion of C. difficile spores.

Blue and red light-induced germination of resting spores in the red-tide diatom Leptocylindrus danicus.

Photophysiological and pharmacological approaches were used to examine light-induced germination of resting spores in the red-tide diatom Leptocylindrus danicus. The equal-quantum action spectrum for photogermination had peaks at about 440 nm (blue light) and 680 nm (red light), which matched the absorption spectrum of the resting spore chloroplast, as well as photosynthetic action spectra reported for other diatoms. DCMU, an inhibitor of photosynthetic electron flow near photosystem II, completely blocked photogermination. These results suggest that the photosynthetic system is involved in the photoreception process of light-induced germination. Results of pharmacological studies of the downstream signal transduction pathway suggested that Ca(2+) influx is the closest downstream neighbor, followed by steps involving calmodulin, nitric oxide synthase, guanylyl cyclase, protein-tyrosine-phosphatase, protein kinase C and actin polymerization and translation.

Kinetics of germination of wet-heat-treated individual spores of Bacillus species, monitored by Raman spectroscopy and differential interference contrast microscopy.

Raman spectroscopy and differential interference contrast (DIC) microscopy were used to monitor the kinetics of nutrient and nonnutrient germination of multiple individual untreated and wet-heat-treated spores of Bacillus cereus and Bacillus megaterium, as well as of several isogenic Bacillus subtilis strains. Major conclusions from this work were as follows. (i) More than 90% of these spores were nonculturable but retained their 1:1 chelate of Ca²+ and dipicolinic acid (CaDPA) when incubated in water at 80 to 95°C for 5 to 30 min. (ii) Wet-heat treatment significantly increased the time, T(lag), at which spores began release of the great majority of their CaDPA during the germination of B. subtilis spores with different nutrient germinants and also increased the variability of T(lag) values. (iii) The time period, ΔT(release), between T(lag) and the time, T(release), at which a spore germinating with nutrients completed the release of the great majority of its CaDPA, was also increased in wet-heat-treated spores. (iv) Wet-heat-treated spores germinating with nutrients had higher values of I(release), the intensity of a spore's DIC image at T(release), than did untreated spores and had much longer time periods, ΔT(lys), for the reduction in I(release) intensities to the basal value due to hydrolysis of the spore's peptidoglycan cortex, probably due at least in part to damage to the cortex-lytic enzyme CwlJ. (v) Increases in T(lag) and ΔT(release) were also observed when wet-heat-treated B. subtilis spores were germinated with the nonnutrient dodecylamine, while the change in I(release) was less significant. (vi) The effects of wet-heat treatment on nutrient germination of B. cereus and B. megaterium spores were generally similar to those on B. subtilis spores. These results indicate that (i) some proteins important in spore germination are damaged by wet-heat treatment, (ii) the cortex-lytic enzyme CwlJ is one germination protein damaged by wet heat, and (iii) the CaDPA release process itself seems likely to be the target of wet-heat damage which has the greatest effect on spore germination.

Phytophthora kernoviae oospore maturity, germination, and infection.

Limited information is known on the basic biology of the recently described Phytophthora kernoviae that produces homothallic oospores. In this study, different P. kernoviae isolates were used to investigate oospore maturity, germination, and infection. All isolates produced oospores in V8 broth at 20°C in the dark by 6d. Oospores also formed at 10 and 15°C, but did not form at 25 and 28°C. Continuous light inhibited oospore production of some isolates but had no negative effect on others. Maturation time of the oospores, as noted by germination and staining with tetrazolium bromide, was not much different among the isolates between 2 and 14 weeks. Oospore germination was optimal at 18 and 20°C, and did not occur at 5, 25, and 30°C. Oospore germination under continuous light was higher than in the dark, but individual isolates showed variable results. Rhododendron leaf disks inoculated with oospores and maintained in the dark at 20°C were necrotic after 1 week, while those kept under continuous light did not develop necrosis. The percentage of leaf disks infected with P. kernoviae was lower in the leaves exposed to continuous light (40%) compared to those kept in the dark (100%).

The molecular and physiological responses of Physcomitrella patens to ultraviolet-B radiation.

Ultraviolet-B (UV-B) radiation present in sunlight is an important trigger of photomorphogenic acclimation and stress responses in sessile land plants. Although numerous moss species grow in unshaded habitats, our understanding of their UV-B responses is very limited. The genome of the model moss Physcomitrella patens, which grows in sun-exposed open areas, encodes signaling and metabolic components that are implicated in the UV-B response in flowering plants. In this study, we describe the response of P. patens to UV-B radiation at the morphological and molecular levels. We find that P. patens is more capable of surviving UV-B stress than Arabidopsis (Arabidopsis thaliana) and describe the differential expression of approximately 400 moss genes in response to UV-B radiation. A comparative analysis of the UV-B response in P. patens and Arabidopsis reveals both distinct and conserved pathways.

Characterization of wet-heat inactivation of single spores of bacillus species by dual-trap Raman spectroscopy and elastic light scattering.

Dual-trap laser tweezers Raman spectroscopy (LTRS) and elastic light scattering (ELS) were used to investigate dynamic processes during high-temperature treatment of individual spores of Bacillus cereus, Bacillus megaterium, and Bacillus subtilis in water. Major conclusions from these studies included the following. (i) After spores of all three species were added to water at 80 to 90 degrees C, the level of the 1:1 complex of Ca(2+) and dipicolinic acid (CaDPA; approximately 25% of the dry weight of the spore core) in individual spores remained relatively constant during a highly variable lag time (T(lag)), and then CaDPA was released within 1 to 2 min. (ii) The T(lag) values prior to rapid CaDPA release and thus the times for wet-heat killing of individual spores of all three species were very heterogeneous. (iii) The heterogeneity in kinetics of wet-heat killing of individual spores was not due to differences in the microscopic physical environments during heat treatment. (iv) During the wet-heat treatment of spores of all three species, spore protein denaturation largely but not completely accompanied rapid CaDPA release, as some changes in protein structure preceded rapid CaDPA release. (v) Changes in the ELS from individual spores of all three species were strongly correlated with the release of CaDPA. The ELS intensities of B. cereus and B. megaterium spores decreased gradually and reached minima at T(1) when approximately 80% of spore CaDPA was released, then increased rapidly until T(2) when full CaDPA release was complete, and then remained nearly constant. The ELS intensity of B. subtilis spores showed similar features, although the intensity changed minimally, if at all, prior to T(1). (vi) Carotenoids in B. megaterium spores' inner membranes exhibited two changes during heat treatment. First, the carotenoid's two Raman bands at 1,155 and 1,516 cm(-1) decreased rapidly to a low value and to zero, respectively, well before T(lag), and then the residual 1,155-cm(-1) band disappeared, in parallel with the rapid CaDPA release beginning at T(lag).

Factors affecting spore germination in algae - review.

This review surveys whatever little is known on the influence of different environmental factors like light, temperature, nutrients, chemicals (such as plant hormones, vitamins, etc.), pH of the medium, biotic factors (such as algal extracellular substances, algal concentration, bacterial extracellular products, animal grazing and animal extracellular products), water movement, water stress, antibiotics, UV light, X-rays, gamma-rays, and pollution on the spore germination in algae. The work done on the dormancy of algal spores and on the role of vegetative cells in tolerating environmental stress is also incorporated.