Valerie R. Flechtner

Phylogeny and Genetic Variance in Terrestrial Microcoleus (Cyanophyceae) Species Based on Sequence Analysis of the 16S rRNA Gene and Associated 16S-23S ITS Region.

Thirty‐one strains of Microcoleus were isolated from desert soils in the United States. Although all these taxa fit the broad definition of Microcoleus vaginatus (Vaucher) Gomont in common usage by soil algal researchers, sequence data for the 16S rRNA gene and 16S–23S internal transcribed spacer (ITS) region indicated that more than one species was represented. Combined sequence and morphological data revealed the presence of two morphologically similar taxa, M. vaginatus and Microcoleus steenstrupii Boye‐Petersen. The rRNA operons of these taxa were sufficiently dissimilar that we suspect the two taxa belong in separate genera. The M. vaginatus clade was most similar to published sequences from Trichodesmium and Arthrospira. When 16S sequences from the isolates we identified as M. steenstrupii were compared with published sequences, our strains grouped with M. chthonoplastes (Mertens) Zanardini ex Gomont and may have closest relatives among several genera in the Phormidiaceae. Organization within the 16S–23S ITS regions was variable between the two taxa. Microcoleus vaginatus had either two tRNA genes (tRNAIle and tRNAAla) or a fragment of the tRNAIle gene in its ITS regions, whereas M. steenstrupii had rRNA operons with either the tRNAIle gene or no tRNA genes in its ITS regions. Microcoleus vaginatus showed no subspecific variation within the combined morphological and molecular characterizations, with 16S similarities ranging from 97.1% to 99.9%. Microcoleus steenstrupii showed considerable genetic variability, with 16S similarities ranging from 91.5% to 99.4%. In phylogenetic analyses, we found that this variability was not congruent with geography, and we suspect that our M. steenstrupii strains represent several cryptic species.

Spirirestis rafaelensis gen. et sp. nov. (Cyanophyceae), a new cyanobacterial genus from arid soils

A new cyanobacterial genus and species, Spirirestis rafaelensis , is described from soils of a semi-arid Utah juniper community in the San Rafael Swell, Utah, U.S.A. Multiple isolates of the organism have only been recovered from well-crusted, protected, and totally undisturbed soils at this site; it has not been recovered from any of the other 40 sites we have examined in the Sonoran, Mojave, Chihuahuan, Colorado Plateau, or Great Basin deserts during the last eight years. Spirirestis shares morphological characters with members of both the Scytonemataceae and Microchaetaceae, principally heterocyte formation, false branching, and presence of sheath. However, unlike the trichomes of all previously described genera in these families, most trichomes of Spirirestis are tightly spiraled. 16S rRNA sequence data suggest that Spirirestis is more closely related to members of the Microchaetaceae than to members of the Scytonemataceae or Rivulariaceae. The data also support the maintenance of Microchaetaceae and Scytonemataceae as separate families.

CRYPTIC SPECIES OF SCENEDESMUS (CHLOROPHYTA) FROM DESERT SOIL COMMUNITIES OF WESTERN NORTH AMERICA

Nine isolates of unicellular green algae were obtained from six geographically separate desert microbiotic crust communities in western North America. Microscopically, eight isolates strongly resembled unicellular forms of Scenedesmus obliquus (Turpin) Kützing. They are oval or crescent shaped, often flattened on one side, with knobby cell apices. SEM indicated a lack of wall ornamentation. Fine filaments connecting cells pole to pole were observed in some isolates, as previously documented in Scenedesmus (Dactylococcus) dissociatus and S. obliquus. The ninth isolate was spherical, without knobby apices or connections between cells, and was similar to unicellular forms that were originally classified as species of Chlorella (Scenedesmus vacuolatus and S. rubescens). None of the isolates formed coenobia in liquid culture. Phylogenetic analysis of the 18S rRNA gene placed all desert isolates in the genus Scenedesmus, separating them into two or three weakly resolved groups along with published sequences of other Scenedesmus isolates. Phylogenetic analyses of the internal transcribed spacer region revealed well‐supported lineages of desert algae that were unsupported with 18S data alone. The eight S. obliquus‐like desert strains formed two distinct clades that excluded the S. obliquus strains from geographically widespread nondesert habitats. The ninth strain was outside of the S. obliquus group, associated with S. raciborskii and S. pectinatus. These results demonstrate three lineages of Scenedesmus from desert soils and provide robust support for the presence of cryptic species in S. obliquus, a morphospecies that is said to have a cosmopolitan distribution. Three new species of Scenedesmus are described.

The Biological Soil Crusts of the San Nicolas Island: Enigmatic Algae from a Geographically Isolated Ecosystem

Abstract Composite soil samples from 7 sites on San Nicolas Island were evaluated quantitatively and qualitatively for the presence of cyanobacteria and eukaryotic microalgae. Combined data demonstrated a rich algal flora with 19 cyanobacterial and 19 eukaryotic microalgal genera being identified, for a total of 56 species. Nine new species were identified and described among the cyanobacteria and the eukaryotic microalgae that were isolated: Leibleinia edaphica, Aphanothece maritima, Chroococcidiopsis edaphica, Cyanosarcina atroveneta, Hassallia californica, Hassallia pseudoramosissima, Microchaete terrestre, Palmellopsis californicus, and Pseudotetracystis compactis. Distinct distributional patterns of algal taxa existed among sites on the island and among soil algal floras of western North America. Some algal taxa appeared to be widely distributed across many desert regions, including Microcoleus vaginatus, Nostoc punctiforme, Nostoc paludosum, and Tolypothrix distorta, Chlorella vulgaris, Diplosphaera cf. chodatii, Myrmecia astigmatica, Myrmecia biatorellae, Hantzschia amphioxys, and Luticola mutica. Some taxa share a distinctly southern distribution with soil algae from southern Arizona, southern California, and Baja California (e.g., Scenedesmus deserticola and Eustigmatos magnus). The data presented herein support the view that the cyanobacterial and microalgal floras of soil crusts possess significant biodiversity, much of it previously undescribed.

Newly revealed diversity of green microalgae from wilderness areas of Joshua Tree National Park (JTNP)

ABSTRACT. Documentation of the biodiversity of eukaryotic algae from desert systems is sparse. Our objective was to characterize microalgae from soil samples collected throughout Joshua Tree National Park, California, USA. Morphological, life-cycle, and DNA sequence data were collected for 100 microalgal isolates distributed over 18 sites in Joshua Tree National Park. Phylogenetic analysis of the 18S rDNA data separated the green algae into 15 major clades—10 in the class Chlorophyceae and 5 in the class Trebouxiophyceae—containing 2 or more lineages plus 9 lineages represented by a single isolate. Five isolates belonging to the class Xanthophyceae and 2 isolates belonging to Eustigmatophyceae were also identified. Some green algal isolates could be placed with confidence in known genera including Bracteacoccus, Chlorosarcinopsis, Myrmecia, Neochlorosarcina, Scenedesmus, and Stichococcus, whereas several green isolates could not be assigned to known genera based on morphological or molecular data. Both morphological and molecular data were important to identifying this biodiversity. Due to the paucity of informative morphological characters, morphology alone does not capture the species diversity found at sites. Molecular data are a richer source of characters with which to identify the algae, but more representative sequences of soil algae are needed in public databases to make identification of any new taxa straightforward. Overall, our data suggest that the biodiversity of these hot deserts still is largely unknown and unexplored.

Algal diversity in North American desert soils

Clonal isolates of cyanophytes were collected from several study sites in the Dugway Proving Ground and San Rafael Sell Overlook in Utah. We identified 32 taxa belonging to 24 cyanobacterial genera. Some taxa were widely distributed, occurring in all sites. For example, the members of the filamentous cyanobacterial genera Leptolyngbya, Microcoleus, Nostoc and Trichocoleus and members of the coccoid genus Aphanocapsa were common to all sites. On the other hand, members of the cyanobacterial genus Calothrix were rarely encountered at the Dugway site but were recovered frequently from the San Rafael site. We were able to compare disturbed and undisturbed sites located close together in the San Rafael Overlook. We found that the genera Spirirestis and Cyanosarcina, were found exclusively in the undisturbed site. A number of the taxa recovered could be identified only to the genus level because they did not match previously published species descriptions. Since we have recovered both prokaryotic eukaryotic taxa new to science in our previous work, it is quite likely that some of these isolates do indeed represent new cyanobacterial species. This study is the most extensive characterization of cyanobacteria from soil crusts in a semi-arid North American deserts. It expands our knowledge of the diversity of the cyanobacterial components of North American soil crusts.

The effect of growth regimen, heat shock and intracellular starch storage on the mating efficiency of Chlamydomonas reinhardtii

The mating efficiency of the non-photosynthetic mutants of Chlamydomonas reinhardtii used in this study is low when gametogenesis is carried out using standard procedures. Alternative procedures were developed to increase mating efficiency of these strains. Gametogenesis of mutant strains is most efficient when vegetative cells are grown on TMAC-N plates for 48–72 h and then in TMAC-1 liquid overnight. One mutant which does not form gametes efficiently under this regimen can be induced to form gametes by exposure to heat-shock at 42·5 or 45°C. The mating efficiencies of starch-storing and starch-negative non-photosynthetic mutant strains were compared. The results show that the ability to store starch intracellularly does not dramatically influence the mating efficiency of the nonphotosynthetic mutant strains.