Experimental associations of cyanobacteria and actinomycetes

Associations of cyanobacteria with actinomycetes are not being investigated. The purpose of this study is to investigate the biological aspects of coexistence of the free-living Anabaena variabilis with actinomycetes isolated from apogeotropic roots of Strangeria eriopus and Cycas micholitzii; with the cyanobacterium Oscillatoria terebriformis (Ag.) Elenk. emend., which were isolated from the natural cyanobacterial mat taken from the Kamchatkan thermal spring; and with actinomycetes isolated from the accumulating culture of cyanobacterium. Positive tropism of actinomycete hyphae to cyanobacterial trichomes and that of the cyanobacterium to streptomycetes were observed. Stimulation of growth of O. terebriformis in the associated culture with the streptomycete was recorded. The increase of fixation of nitrogen by A. variabilis and of photosynthetic activity of O. terebriformis in the associated culture with the streptomycete was recorded.     

High selectivity in symbiotic associations of lichenized ascomycetes and cyanobacteria

The selectivity of mycobionts and cyanobionts in lichen symbioses were examined. We analyzed symbiotic cyanobionts, collected from different sample sites, and compared them to free‐living cyanobacteria Nostoc. Cyanobionts were obtained from lichens assigned to the genera Pseudocyphellaria and Sticta, in particular. Multiple gene loci were screened and direct optimization was used in the phylogenetic analyses. We show that many lichen fungi are strongly selective towards their cyanobionts. Lichenized ascomycetes seem to be able to identify and choose a specific strain, species or a species group of Nostoc with which to associate. The present analyses also suggest that some of the Nostoc taxa may be specialized in symbiotic life with only lichenized ascomycetes. Despite the selectivity observed in fungi, there appears to be no coevolution between the partners. We have also discussed the problems of using the tRNA^Leu intron as a marker in phylogenetic analyses. © The Willi Hennig Society 2006.     

Morphological and physiological modifications of Cistus salvifolius L. winter leaves in response to the rise in winter temperatures

The global climate is predicted to change in the next century; for the Mediterranean Basin, an increase in air temperature more than 4°C and a higher frequency of extreme climatic events such as drought and heat waves are expected. In this work, the response of Cistus salvifolius L. to the rise in winter temperature has been studied. Plants acclimated to winter conditions [outdoor (OUT)] were moved into a greenhouse [indoor (IND)] at higher temperature and eco-physiological behaviour was analysed on leaves after 15 days from plant transferring (IND_15d) and on leaves developed IND. IND leaves were characterized by reduced thickness, higher specific leaf area, higher CO₂ mesophyll conductance and photosynthetic rate, and lower respiratory rate than leaves grown OUT upon current winter conditions. In IND_15d leaves, no improvement of photochemical activity was found. When IND leaves were subjected to a rapid increase in air temperature, the CO₂ fixation was not limited indicating a high thermotolerance of photosynthetic machinery. The results for IND leaves indicate the occurrence of a strategy that merging changes in leaf structure as well as in photosynthetic regulation allow C. salvifolius to maintain an elevated carbon gain in response to temperature increase.     

Morphological and phylogenetic diversity of thermophilic cyanobacteria in Algerian hot springs

Geothermal springs in Algeria have been known since the Roman Empire. They mainly locate in Eastern Algeria and are inhabited by thermophilic organisms, which include cyanobacteria forming mats and concretions. In this work, we have investigated the cyanobacterial diversity of these springs. Cyanobacteria were collected from water, concretions and mats in nine hot springs with water temperatures ranging from 39 to 93 °C. Samples were collected for isolation in culture, microscopic morphological examination, and molecular diversity analysis based on 16S rRNA gene sequences. Nineteen different cyanobacterial morphotypes were identified, the most abundant of which were three species of Leptolyngbya, accompanied by members of the genera Gloeocapsa, Gloeocapsopsis, Stigonema, Fischerella, Synechocystis, Microcoleus, Cyanobacterium, Chroococcus and Geitlerinema. Molecular diversity analyses were in good general agreement with classical identification and allowed the detection of additional species in three springs with temperatures higher than 50 °C. They corresponded to a Synechococcus clade and to relatives of the intracellularly calcifying Candidatus Gloeomargarita lithophora. The hottest springs were dominated by members of Leptolyngbya, Synechococcus-like cyanobacteria and Gloeomargarita, whereas Oscillatoriales other than Leptolyngbya, Chroococcales and Stigonematales dominated lower temperature springs. The isolation of some of these strains sets the ground for future studies on the biology of thermophilic cyanobacteria.     

Identification, regulation and physiological functions of multiple NADPH dehydrogenase complexes in cyanobacteria

Cyanobacteria possess multiple, functionally distinct NADPH dehydrogenase (NDH-1) complexes. In this mini-review, we describe the cyanobacterial NDH-1 complexes by focusing on their identification, regulatory properties, and multiple functions. The multiple functions can be divided into basic and extending functions, and the basic functions are compared with those in chloroplasts. Many questions related to cyanobacterial NDH-1 complexes remain unanswered and are briefly summarized here.     

Identification,regulation and physiological functions of multiple NADPH dehydrogenase complexes in cyanobacteria

Cyanobacteria possess multiple,functionally distinct NADPH dehydrogenase (NDH-1) complexes.In this mini-review,we describe the cyanobacterial NDH-1 complexes by focusing on their identification,regulatory properties,and multiple functions.The multiple functions can be divided into basic and extending functions,and the basic functions are compared with those in chloroplasts.Many questions related to cyanobacterial NDH-1 complexes remain unanswered and are briefly summarized here.     

Fluorescence as a probe for physiological integrity of freshwater cyanobacteria

The effects of energetic decoupling of phycobiliproteins (PBP) from photosystems in Nostoc sp. on the emission characteristics and fluorescence profiles of cyanobacterial photosynthetic apparatus and its components were studied using steady-state and time-resolved fluorescence emission. The steady-state measurements show a rise in fluorescence from PBP released at low ionic strength. The emission decay profile of Nostoc photosynthetic apparatus has two components with lifetimes 1.8 ns and about 0.1 ns but their relative contributions to the total emission decay vary, depending on the energetic coupling of phycobilisomes to photosystems. At low ionic strength, the contribution of the long-lived emission characteristic for free phycocyanin increased, confirming the detachment of PBP from the photosystems. We show that these effects can be used as a basis for improvement of cyanobacteria detection method. It is demonstrated that the fitting algorithm applied in the measurements with a FluoroProbe fluorometer (bbe Moldaenke, Schwentinental, Germany) can differentiate between coupled and uncoupled PBP. This approach may prove useful in monitoring the state of photosynthetic apparatus in cyanobacterial populations and their spatial distribution in water reservoirs.     

Morphological and isotopic changes of heterocystous cyanobacteria in response to N2 partial pressure

Earth's atmospheric composition has changed significantly over geologic time. Many redox active atmospheric constituents have left evidence of their presence, while inert constituents such as dinitrogen gas (N₂) are more elusive. In this study, we examine two potential biological indicators of atmospheric N₂: the morphological and isotopic signatures of heterocystous cyanobacteria. Biological nitrogen fixation constitutes the primary source of fixed nitrogen to the global biosphere and is catalyzed by the oxygen‐sensitive enzyme nitrogenase. To protect this enzyme, some filamentous cyanobacteria restrict nitrogen fixation to microoxic cells (heterocysts) while carrying out oxygenic photosynthesis in vegetative cells. Heterocysts terminally differentiate in a pattern that is maintained as the filaments grow, and nitrogen fixation imparts a measurable isotope effect, creating two biosignatures that have previously been interrogated under modern N₂ partial pressure (pN₂) conditions. Here, we examine the effect of variable pN₂ on these biosignatures for two species of the filamentous cyanobacterium Anabaena. We provide the first in vivo estimate of the intrinsic isotope fractionation factor of Mo‐nitrogenase (ε_fix = ?2.71 ± 0.09‰) and show that, with decreasing pN₂, the net nitrogen isotope fractionation decreases for both species, while the heterocyst spacing decreases for Anabaena cylindrica and remains unchanged for Anabaena variabilis. These results are consistent with the nitrogen fixation mechanisms available in the two species. Application of these quantifiable effects to the geologic record may lead to new paleobarometric measurements for pN₂, ultimately contributing to a better understanding of Earth's atmospheric evolution.     

Morphological, physiological and taxonomic studies of Bacillus azotoformans

Seventeen strains of the new species Bacillus azotoformans were isolated by enrichment culture in peptone broth inoculated with pasteurized soil and then incubated under N2O at 32 degrees C. The bacterium is a Gram-negative rod, motile with peritrichous flagella, which produces oval spores without exosporia in swollen sporangia. However, the cells have thick walls, mesosomes, and persistent septa characteristic of Gram-positive bacteria. The bacterium lacks fermentative activity, does not attack carbohydrates, has complex growth requirements, and will grow anaerobically only if one of the following electron acceptors is present: NO3-, NO2-, N2O, S4O6--, or fumarate. Nitrate, nitrite, and nitrous oxide are denitrified with the production of N2. The microorganism is mesophilic, gives a positive oxidase reaction, synthesizes a type c cytochrome, and does not hydrolyse gelatin, starch, or "Tween 80." Poly-beta-hydroxybutyric acid is snythesized when the bacterium is grown in a medium containing DL-3-hydroxybutyrate. The following enzymes are present: nitrate reductase A, respiratory nitrite reductase, tetrathionate and fumarate reductases, and L-glutamate dehydrogenase. The following enzymes are absent: thiosulfate reductase, urease, lecithinase, arginine dihydrolase, phenylalanine deaminase, and catalase. For the 17 strains, the mean value of the G = C percent of the DNA is 39.8 +/- 1.2. All the strains are highly similar.     

Morphological and physiological sexual selection targets in a territorial damselfly

• 1 Several morphological and physiological traits may shape fitness through the same performance measure. In such cases, differentiating between a scenario of many‐to‐one mapping, where phenotypic traits independently shape fitness leading to functional redundancy, and a scenario where traits strongly covary among each other and fitness, is needed.
• 2 A multivariate approach was used, including morphological and physiological traits related to flight ability, a crucial performance measure in flying insects, to identify independent correlates of short‐term mating success (mated versus unmated males) in the territorial damselfly Lestes viridis.
• 3 Males with higher flight muscle mass, higher relative thorax mass, and more symmetrical hindwings, all traits presumably linked to manoeuvrability, were more likely to be mated. Unexpectedly, although relative thorax mass is often used as a proxy for flight muscle mass, both traits were selected for independently. Mated males had a higher thorax fat content than unmated males, possibly because of enhanced flight endurance.
• 4 The finding of several independent targets of sexual selection linked to flight ability is consistent with a scenario of many‐to‐one mapping between phenotype and performance. Identifying such a scenario is important, because it may clarify situations where animals may show suboptimal values for some phenotypic traits shaping a performance measure, while still having high performance and fitness. We argue in the discussion that the functional approach of sexual selection provides a potent tool for examining unresolved issues in both sexual selection theory, as well as life‐history theory.