THE EFFECT OF SULFIDE ON THE BLUEGREEN ALGAE OF HOT SPRINGS. I. NEW ZEALAND AND ICELAND1

The concentration of soluble sulfide (H₂S, HS^?, S⁼)² in hot springs of New Zealand and Iceland has a “species-determining” effect which appears to override the effect of all other chemical factors excepting hydrogen ion concentration. The cosmopolitan high-temperature form (HTF) of Mastigocladus laminosus (Ag.) Cohn appears to be sensitive to concentrations of S⁼ over 0.15 mg·l^?1 in New Zealand and 0.25 mg·l^?1 in Iceland. It was absent in thermal streams where S⁼ level was high enough to exceed this concentration at a point below its optimal temperature range (i.e., below ca. 50 C). In low or non-S⁼ springs in these regions this alga formed mats to an upper temperature limit of 63–64 C. In contrast, one bluegreen alga (Oscillatoria amphigranulata van Goor) occurred abundantly only in moderate to high S⁼ springs of New Zealand; this was a species with an upper temperature limit of about 57 C. Field ¹⁴C-HCO₃^? incorporation experiments with various levels of added S⁼ confirmed the sensitivity of HTF Mastigocladus and the great tolerance of O. amphigranulata. In the latter, the photosynthetic incorporation of ¹⁴C-HCO₃^? was sustained or enhanced by the additions of S⁼ in the presence of 5 × 10^?5m DCMU, an inhibitor of photoelectron transport on the reducing side of photosystem II. It is possible, but not proven, that S⁼ may act as a photoreductant in this species.     

MORPHOLOGY OF DNA CONTAINING STRUCTURES (NUCLEOIDS) AS A PROSPECTIVE CHARACTER IN CYANOPHYTE TAXONOMY1

DNA containing structures (nucleoids) were visualized by 4′, 6-diamidino-2-phenylindole (DAPI) fluorescent staining in two groups of cyanophytes (59 filamentous oscillatorialean species and 12 coccal Synechococcus-like organisms) to test the possibility of using nucleoid morphology in cyanophyte taxonomy. The morphology of nucleoids (size, shape, and structure) in oscillatorialean species is specific for individual families. The morphology of the nucleoid in Synechococcus-like species agrees from the proposed separation of the genus Cyanothece from Synechococcus. A much different nucleoid morphology in three species of Cyanothece suggests that these species should be separated into a new genus. On the basis of other characters, the species could be returned to the genus Cyanobacterium. My results indicate that the morphology of nucleoids is a valuable character in the classification of the cyanophytes examined; thus, it is a prospective feature that could be used in the taxonomy of other groups of cyanophytes. Additionally, DAPI staining is not a complicated procedure. The new character is easy to see in samples taken from nature, both living and preserved.     

Diversity in the influence of temperature on the growth rates of freshwater algae, and its ecological relevance

1. Growth rates of seven species of planktonic algae were determined in culture over a range of temperature from 2 to 35 °C. Additional observations on growth and viability were made for 13 species in the temperature range 20–35 °C. 2. There was a wide range of growth rates between species at their optimal temperatures, from 1.7 divisions day^?1 (Asterionella formosa) to 0.3 divisions day^?1 (Ceratium furcoides). 3. There were considerable differences between species for growth at low and high temperature. Certain algae, including the diatom A. formosa and the flagellates Cryptomonas marssonii, Dinobryon divergens and Eudorina unicocca var. unicocca, had growth rates of 0.4 divisions day^?1 or more at 5 °C. The cyanophyte Tychonema (formerly Oscillatoria) bourrellyi, the xanthophyte Tribonema sp., the desmid Staurastrum cingulum and the large dinoflagellate C. furcoides grew poorly or not at all at this temperature. All 21 species tested could grow at 25 °C, but many – including most of the diatoms, some cyanophytes, and all the flagellates – failed to grow persistently at 30 °C. Only Aphanizomenon flos‐aquae survived with moderate increase at 35 °C, a lethal temperature for the other species. 4. The applicability was considered of proposed quantitative formulations of the rate‐temperature relationship. Simple exponential relationships applied only to very limited lower ranges of temperature. The relationship proposed by B?lehrádek was a better fit over a wider temperature range, but still excluded rate‐decline at high temperature. 5. The interspecific differences found are of potential significance for restrictions in natural distributions associated with season, altitude (especially above 500 m) and latitude.     

LOTIC ALGAL COMMUNITIES IN THE MT. ST. HELENS REGION SIX YEARS FOLLOWING THE ERUPTION1

A survey of 21 lotic habitats from the Mt. St. Helens region, Washington, was conducted during late summer 1986, six years after the eruption. A total of 152 taxa was observed (94 diatoms, 36 chlorophytes, 19 cyanophytes, 2 xanthophytes, and I rhodophyte). Sampling sites were classified by TWINSPAN (two-way indicator species analysis) and ordinated by DECORANA (detrended correspondence analysis). In general, both techniques corresponded well with each other and grouped sites according to the intensity of disturbance that they experienced. Species richness and diversity values tended to be lowest at the most heavily disturbed sites. Chlorophyll a values ranged over two orders of magnitude and tended to be higher at sites sampled from small, low-discharge tributaries. Loowit Creek, a thermally influenced stream that begins within the volcanic crater, was dominated by thick mats of the cyanophyte Mastigocladus laminosus. A general comparison of the present study with one conducted just after Mt. St. Helens erupted suggests that successional processes are operating in these lotic algal communities.     

Genetic Diversity among Thermophilic Bacteria Isolated from Geothermal Sites by Using Two PCR Typing Methods

Microbial communities thriving at two hot springs, Hammam Pharaon (Pharaoh's Bath) and Oyoun Mossa (Moses springs), in Egypt was studied by cultural and molecular methods. Thirteen morphologically distinct strains of facultative anaerobic thermophilic bacterial isolates have been characterized and identified using phenotypic and genotypic characters including RAPD-PCR, ERIC-PCR typing, plasmid analysis and 16S rRNA sequencing. All isolates produced plasmid DNA with various sizes ranging from 0.7 kb to a larger plasmid 7.2 kb. The bacterial strains could tolerate a temperature range between 45 to 85°C and a pH between 4–11. Also, sulphate-reducing bacteria (SRB) in the thermal springs were investigated with combined biochemical and molecular approaches. A sulphate-reducing bacteria medium containing lactate was used for enrichment and isolation, which yielded Gram negative, rod shaped, anaerobic, non-spore-forming and motile bacteria capable of reducing sulphate to sulphide. These grew at temperatures ranging from 30 to 50°C and could use pyruvate, lactate and ethanol as electron donors. The dissimilatory sulphite reductase (DSR) gene sequences of eleven representative isolates revealed that the strains belonged to the sulphur reducing bacterial species Desulfovibrio vulgaris. 16S rRNA gene partial sequence results indicated the presence of novel or existing species of Bacillus (one species), Anoxybacillus (four species) and Geobacillus (eight species). In this study phenotypic and genotypic diversity were applied for the first time to differentiate thermophilic bacteria of such geothermal sites in Sinai, Egypt.     

Megaplasmids in Thermus oshimai isolates from two widely separated geographical areas: restriction fragment profiling and DNA homology

Megaplasmid DNA was detected in ten isolates belonging to the recently described thermophilic eubacterial species Thermus oshimai and isolated from hot springs in Portugal (eight isolates) and Iceland (two isolates). The estimated size of the large plasmids purified from T. oshimai SPS-18 from S. Pedro do Sul, Portugal, and from isolate JK-91 from Hveragerdhi-Hengill, Iceland, was 214 and 275 kb, respectively. No sequence homologous to isolate SPS-18 megaplasmid is present in chromosomal DNA as indicated by Southern hybridization analysis. Overall examination of the HindIII fragment profiles of megaplasmid DNAs purified from isolates from the same geographical area gave similar but not always identical restriction profiles on agarose gels. Restriction fragment length polymorphism (RFLP) was higher for megaplasmids present in isolates purified from the Portuguese and Icelandic isolates than for megaplasmids from the same hot spring. Megaplasmid RFLP correlated with previous results obtained on the polymorphism of macrorestriction patterns of whole genomic DNA and with the RFLP of co-resident small plasmid DNA that was found in one half of the isolates examined. The 16-kb HindIII–HindIII fragment from isolate SPS-18 megaplasmid showed DNA–DNA homology with restriction fragments of similar size generated by the large plasmids present in all the other isolates, even in those from hot springs of widely separated geographical areas. This suggests a high degree of sequence conservation in T. oshimai megaplasmids. Received: 12 May 1997 / Accepted: 17 July 1997     

ASSOCIATION OF PLEUROCAPSA AND CALOTHRIX (CYANOPHYTA) IN A THERMAL STREAM1,2

A crustose, nodular mat, primarily composed of Calothrix sp. and Pleurocapsa sp., occurs in some alkaline hot springs of the western United States. Together, these species constituted ca. 71% of the mat biomass; the remainder was partitioned between other cyanophytes and bacteria. Their temperature growth ranges in culture were 24–50 C (Calothrix) and 30–55 C (Pleurocapsa). Both clonal cultures had maximal growth rates at 45 C (Pleurocapsa, 1.28 doublings/24 h; Calothrix 2.30). Calothrix grew at approximately twice the rate of Pleurocapsa throughout their coincidental temperature range. The relative proportions of Calothrix (42%) and Pleurocapsa (27%) were constant in a thick mat (ca. 1 mm) regardless of season; however, a thin mat (ca. 0.5 mm) contained significantly more Pleurocapsa (71%) and less Calothrix (5%). Analysis of 10 μm thick microtome sections showed that Pleurocapsa dominated the innermost region (substrate side) of the nodule mat while Calothrix abundance increased from ca. 3% in this region to 80–96% at the surface of thick mat samples (ca. 0.8–2.3 mm). Our proposed that the grazing pressure exerted by an ostracod population accounts for the continued coexistence of and the observed spatial relationships between these species appears most consistent with the observations.     

Effects of mixing and silica enrichment on phytoplankton seasonal succession

During the summer of 1983, cryptophytes, diatoms, cyanophytes, and the dinoflagellate, Ceratium hirundinella were most prominant among the phytoplankton of Eau Galle Reservoir. In the open water, cryptophytes and diatoms peaked in the spring, cyanophytes were most successful in the early summer, and Ceratium was dominant from mid-July until early August. In general, the sequence of events corresponded quite closely to the model of seasonal succession developed by the Plankton Ecology Group of the International Society of Limnology. To a large extent, the same pattern held in four experimental water columns. Departures from the model involved the roles of specific nutrients in diatom and cyanophyte periodicity. Diatoms began to yield to cyanophytes in late spring despite intermittent mixing and silica enrichment. Although capable of buoyancy regulation and thus well adapted to stable water columns, cyanophytes had greater increases in biomass in mixed columns, and in those columns, were most successful during a period of intermittent mixing. Cyanophyte success varied inversely with TN : TP ratios during the period of intermittent mixing, but not subsequently. By mid-July, Ceratium dominated the phytoplankton of every column except that of a mixed column in which conditions favored cyanophytes and large diatom species.     

Winter survival of Ceramica pisi (Lepidoptera: Noctuidae) in Iceland

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THE EFFECTS OF SOME ECOLOGICAL FACTORS ON CELL SIZE OF THE HOT SPRING ALGA SYNECHOCOCCUS LIVIDUS (CYANOPHYTA)1

Algae were sampled along temperature gradients of 30 thermal springs in Colorado, Idaho, Montana and Wyoming. From a maximum temperature of 74.5 C downstream, to ca. 62 C, the diversity of the algae was limited to the various forms of Synechococcus lividus Copeland; from ca. 62 to 40–45 C it coexisted with other algae. When S. lividus was in direct sunlight the mean length was greatest at the highest temperatures of its existence, becoming shorter as the water cooled; the mean reduction in length was 0.132 μm for each 1 C reduction in temperature. The cells in a shaded stream did not exhibit the reduction in size with reduced temperature, but remained about the same length from 73 C downstream to 45 C. The longer cells from the highest temperatures of their existence in any stream could not become established in the cooler water downstream, so the range of cell lengths (diversity) became less as the water cooled. Unknown dissolved substance(s) depressed the upper temperature limit in two streams and had a reverse effect on the expected length–temperature relationship; the shortest cells were at the higher temperatures. Generally, total dissolved substances had a positive effect on the length; the longest cells were in the water with the highest total dissolved solids (TDS) at the upper temperature limits of 70–74.5 C. In the temperature range of 55–60 C the higher TDS were not as effective in developing longer cells.     

CYANOPHYTE CEPHALODIA IN THE LICHEN GENUS NEPHROMA

The lichens, Nephroma expallidum (Nyl.) Nyl. and N. arcticum (L.) Torss., consistently have at least two symbionts in a single thallus: a green alga in the algal layer and a blue-green alga in the internal cephalodia. The cephalodia originate from algal cells in contact with the lower surface of the lichen, in the zone of rhizine formation. The rhizines surround the epiphytic algal colony and form a second cortical layer; following dissociation of the original lower cortex, further growth of the two organisms results in the cyanophyte colony being enveloped by a compact layer of fungal tissue and positioned in the lichen medulla. The colony may eventually assume a superior or inferior position in relation to the lichen thallus, depending in part on the lichen species. Nephroma anticum may have two distinct morphological forms of blue-green algae in the same thallus and occasionally in the same cephalodium. It appears that the relationship that exists between the cephalodial algae and the lichen thallus is antagonistic and results, in some cases, in the exclusion of the green algal layer and death to the cephalodial cyanophytes.     

Maximum thermal tolerance trades off with chronic tolerance of high temperature in contrasting thermal populations of Radix balthica

Thermal adaptation theory predicts that thermal specialists evolve in environments with low temporal and high spatial thermal variation, whereas thermal generalists are favored in environments with high temporal and low spatial variation. The thermal environment of many organisms is predicted to change with globally increasing temperatures and thermal specialists are presumably at higher risk than thermal generalists. Here we investigated critical thermal maximum (CT_max) and preferred temperature (T_p) in populations of the common pond snail (Radix balthica) originating from a small‐scale system of geothermal springs in northern Iceland, where stable cold (ca. 7°C) and warm (ca. 23°C) habitats are connected with habitats following the seasonal thermal variation. Irrespective of thermal origin, we found a common T_p for all populations, corresponding to the common temperature optimum (T_opt) for fitness‐related traits in these populations. Warm‐origin snails had lowest CT_max. As our previous studies have found higher chronic temperature tolerance in the warm populations, we suggest that there is a trade‐off between high temperature tolerance and performance in other fitness components, including tolerance to chronic thermal stress. T_p and CT_max were positively correlated in warm‐origin snails, suggesting a need to maintain a minimum “warming tolerance” (difference in CT_max and habitat temperature) in warm environments. Our results highlight the importance of high mean temperature in shaping thermal performance curves.     

Occurrence of Sulfolobus acidocaldarius,an extremely thermophilic acidophilic bacterium,in New Zealand hot springs

Several hot springs in the Rotorua-Taupo regions, North Island, New Zealand, were tested for the presence of extremely thermophilic acidophilic bacteria. In the majority of the springs, ranging in temperature from 43–96°C and in pH from 2.1–6.9, direct microscopic observations revealed the presence of both rod-shaped and spherical bacteria. Isolations were attempted at 70°C and pH 2.0 and 7.0, with either yeast extract for heterotrophic growth, or elemental sulfur as the sole source of energy for autotrophic growth. Eight of the samples produced grwoth at pH 2.0 with either yeast extract or sulfur, but none of the samples grew at pH 7.0. All the isolates obtained, resembled Sulfolobus acidocaldarius, a thermophilic acidophilic bacterium which has previously been reported from various regions in the Northern Hemisphere. Immunofluorescence examination of six of these isolates revealed varying degrees of cross reactions with two already characterized Sulfolobus isolates from the Yellowstone National Park, U.S.A. This paper is the first published record of Sulfolobus from the Southern Hemisphere.     

An unusual cyanobacterium from saline thermal waters with relatives from unexpected habitats

Cyanobacteria that grow above seawater salinity at temperatures above 45°C have rarely been studied. Cyanobacteria of this type of thermo-halophilic extremophile were isolated from siliceous crusts at 40–45°C in a geothermal seawater lagoon in southwest Iceland. Iceland Clone 2e, a Leptolyngbya morphotype, was selected for further study. This culture grew only at 45–50°C, in medium ranging from 28 to 94 g L⁻¹ TDS, It showed 3 doublings 24 h⁻¹ under continuous illumination. This rate at 54°C was somewhat reduced, and death occurred at 58°C. A comparison of the 16S rDNA sequence with all others in the NCBI database revealed 2 related Leptolyngbya isolates from a Greenland hot spring (13–16 g L⁻¹ TDS). Three other similar sequences were from Leptolyngbya isolates from dry, endolithic habitats in Yellowstone National Park. All 6 formed a phylogenetic clade, suggesting common ancestry. These strains shared many similarities to Iceland Clone 2e with respect to temperature and salinity ranges and optima. Two endolithic Leptolyngbya isolates, grown previously at 23°C in freshwater medium, grew well at 50°C but only in saline medium. This study shows that limited genotypic similarity may reveal some salient phenotypic similarities, even when the related cyanobacteria are from vastly different and remote habitats.     

Heliobacterium modesticaldum,sp. nov., a thermophilic heliobacterium of hot springs and volcanic soils

Enrichment cultures for heliobacteria at 50°C yielded several strains of a thermophilic heliobacterium species from Yellowstone hot spring microbial mats and volcanic soils from Iceland. The novel organisms grew optimally above 50°C, contained bacteriochlorophyll g, and lacked intracytoplasmic membranes. All isolates were strict anaerobes and grew best as photoheterotrophs, although chemotrophic dark growth on pyruvate was also possible. These thermophilic heliobacteria were diazotrophic and fixed N₂ up to their growth temperature limit of 56°C. Phylogenetic studies showed the new isolates to be specific relatives of Heliobacterium gestii and, as has been found in H. gestii, they produce heat-resistant endospores. The unique assemblage of properties found in these thermophilic heliobacteria implicate them as a new species of this group, and we describe them herein as a new species of the genus Heliobacterium, Heliobacterium modesticaldum.     

Planktic cyanophytes and their ecology in the shallow Lake Mikri Prespa, Greece

Cyanophytes dominated the phytoplankton of shallow Lake Mikri Prespa during the period May 1990 to September 1992 (76.5 and 52.0% of the total phytoplankton biomass in 1990–1991 and 1991–1992, respectively). Biomass peaks were observed in autumn (from 5.2 to 34.5 g m^-3) when low dissolved inorganic nitrogen, high phosphate phosphorus and low Z_cu to Z_mix ratio prevailed. The dominant species were Microcystis aeruginosa and M. wesenbergii. These represented 64 and 86% of the cyanophyte biomass in 1990–1991 and 1991–1992, respectively and revealed similar patterns of seasonality forming biomass peaks in late summer - autumn. Small chroococcalean cyanophytes (< 2 μm) showed also similar temporal distributions. Of the filamentous cyanophytes, the most important species was Anabaena lemmermannii var. minor which formed peaks in late summer and autumn (2.6 and 1.1 g m^-3 in 1990 and 1992, respectively). Rainfall and the N:P ratio were probably the main factors influencing the seasonality of all of the filamentous cyanophytes in the lake. Cyanophytes, tended to increase at temperatures higher than 16 °C and at inorganic nitrogen concentrations lower than 100 μg 1^--¹. The frequent mixing of the water column did not seem to prohibit the substantial increase of the group.     

Genomic and Functional Diversity of Bacteria Isolated from Hot Springs in Odisha,India

This study focused on culture-dependent survey of important bacterial community diversity of hot springs of Odisha. India. Molecular and cultural techniques were employed for assessing and exploiting the genetic and functional variability among the isolates obtained from three alkaline and mesophilic hot springs. A total of 48 isolates belonging to family Bacillaceae, Paenibacillaceae, Planococcaceae, Pseudomonadaceae and Enterobacteriaceae were identified. Majority of the bacterial isolates were affiliated with the genus Bacillus. Morphologically all the isolated bacteria were either Gram-positive spore-forming rods, or Gram-negative rods. The optimum temperature for growth of the isolates varied between 37°C to 50°C. The functional diversity revealed that many of the predominant and scarce isolates produced a variety of extracellular enzymes such as amylase, cellulase, lipase, phosphatase and protease, and genus Bacillus dominated for extracellular enzymatic activity. We employed two molecular markers to characterize the isolates. The hsp60 universal target sequence was found to be more discriminatory than 16s rRNA gene sequences. The cultivable bacterial community structure that colonized in the investigated thermal springs did not reveal much overlapping. Our results indicate that bacteria in the geothermal environment are metabolically active and cultivable populations may have great potential in biotechnology.     

Distribution of Thermus spp. in Icelandic Hot Springs and a Thermal Gradient

The growth range in nature of bacteria belonging to the genus Thermus was investigated by sampling 55 different hot springs in Iceland. The springs ranged in temperature from 32 to 99°C, and in pH from 2.1 to 10.1. Viable counts of Thermus spp. ranging from 10 to 10⁴ CFU/100 ml of spring water were found in 27 of the springs sampled. The temperature range for these bacteria was found to be 55 to 85°C, and the pH range was from about 6.5 to above 10. Thermus spp. were found in springs containing up to 1 mM dissolved sulfide and having conductivity up to 2,000 μS/cm. The distribution of Thermus spp. in a hot spring thermal gradient was also investigated and found to agree well with the overall distribution in individual springs.     

Thermal ecotypes of amphi-Atlantic algae. I. Algae of Arctic to cold-temperate distribution (Chaetomorpha melagonium,Devaleraea ramentacea andPhycodrys rubens)

Three species of Arctic to cold-temperate amphi-Atlantic algae, all occurring also in the North Pacific, were tested for growth and/or survival at temperatures of −20 to 30°C. When isolates from both western and eastern Atlantic shores were tested side-by-side, it was found that thermal ecotypes may occur in such Arctic algae.Chaetomorpha melagonium was the most eurythermal of the 3 species. Isolates of this alga were alike in temperature tolerance and growth rate but Icelandic plants were more sensitive to the lethal temperature of 25°C than were more southerly isolates from both east and west. With regard toDevaleraea ramentacea, one Canadian isolate grew extraordinarily well at −2 and 0°C, and all tolerated temperatures 2–3°C higher than the lethal limit (18–20°C) of isolates from Europe. ConcerningPhycodrys rubens, both eastern and western isolates died at 20°C but European plants tolerated the lethal high temperature longer, were more sensitive to freezing, and attained more rapid growth at optimal temperatures. The intertidal species,C. melagonium andD. ramentacea, both survived freezing at −5 and −20°C, at least for short time periods.C. melagonium was more susceptible thanD. ramentacea to desiccation. Patterns of thermal tolerance may provide insight into the evolutionary history of seaweed species.     

Carbon:chlorophyll <Emphasis Type="Italic">a</Emphasis> ratio,assimilation numbers and turnover times of Lake Kinneret phytoplankton

Carbon to chlorophyll a (C:Chl) ratios, assimilation numbers (A.N.) and turnover times of natural populations of individual species and taxonomic groups were extracted from a long-term database of phytoplankton wet-weight biomass, chlorophyll a concentrations, and primary production in Lake Kinneret, Israel. From a database spanning more than a decade, we selected data for samples dominated by a single species or taxonomic group. The overall average of C:Chl was highest for cyanophytes and lowest for diatoms, while chlorophytes and dinoflagellates showed intermediate values. When converting chlorophyll a to algal cellular carbon this variability should be taken into account. The variability in C:Chl within each phylum and species (when data were available) was high and the variability at any particular sampling date tended to be greater than the temporal variability. The average chlorophyll a-normalized rate of photosynthetic activity of cyanophytes was higher and that of the dinoflagellates lower than that of other phyla. Turnover time of phytoplankton, calculated using primary productivity data at the depth of maximal photosynthetic rate, was longest in dinoflagellates and shortest in cyanophytes, with diatoms and chlorophytes showing intermediate values. The more extreme C:Chl and turnover times of dinoflagellates and cyanobacteria in comparison with chlorophytes and diatoms should be taken into consideration when employed in ecological modeling.