Phytophthora parsiana sp. nov., a new high-temperature tolerant species

As part of a study to examine the phylogenetic history of the taxonomically challenging species Phytophthora cryptogea and P. drechsleri, a distinct monophyletic group of isolates, previously described as P. drechsleri or P. cryptogea, were characterised. Analysis of their rDNA ITS sequences indicated that these isolates were distinct from P. drechsleri, P. cryptogea, and all members of Phytophthora ITS clades 1–8, clustering instead alongside basal groups previously described as clades 9 and 10. This group comprised six isolates all of which were isolated from woody plants, such as pistachio (Pistacia vera, Iran and USA), fig (Ficus carica, Iran), and almond (Prunus dulcis, Greece). Analysis of sequence data from nuclear (β-tubulin and translation elongation factor 1α) and mitochondrial (cytochrome c oxidase subunit I) genes confirmed the ITS-based analysis as these isolates formed a distinct monophyletic group in all NJ trees. The isolates were fast growing with a relatively high optimum growth temperature of 30 °C and, in most cases, rapid colony growth even at 37 °C. The isolates produced complex colony patterns on almost all media, especially corn meal agar (CMA). Phylogenetic analysis and examination of all the other morphological and physiological data lead us to infer that this taxon has not been described previously. As this taxon was first isolated and described from Iran we propose that this taxon be formally designated as Phytophthora parsiana.     

Growth of dinoflagellates, Ceratium furca and Ceratium fusus in Sagami Bay, Japan: The role of temperature, light intensity and photoperiod

Seasonal changes of field populations and growth rates of two dinoflagellates, Ceratium furca and Ceratium fusus, were examined in the temperate coastal water of Sagami Bay, Japan. Weekly field sampling was conducted from August 2002 to August 2003, and laboratory experiments were also carried out to investigate effects of temperature, irradiance and photoperiod on the growth rates of these two Ceratium species. In the field, the abundances of both species increased significantly from April to August 2003, were gradually decreased from November 2002 and were not observed in January 2003. C. fusus was able to increase at lower temperatures in February 2003 compared to C. furca. In the laboratory, the two species did not grow at <10 °C or >32 °C. The highest specific growth rate of C. furca was 0.72 d⁻¹ at 24 °C and 600 μmol m⁻² s⁻¹. Optimum growth rates (>0.4 d⁻¹) of C. furca were observed at temperatures from 18 to 28 °C and at irradiances from 216 to 796 μmol m⁻² s⁻¹. The highest growth rate of C. fusus was 0.56 d⁻¹ at 26 °C and 216 μmol m⁻² s⁻¹. Optimum growth rates of C. fusus were observed at the same irradiance rage of C. furca, whereas optimum temperature range was narrower (26–28 °C). The growth curves of both species indicated saturation of the growth rates when light intensity was above 216 μmol m⁻² s⁻¹, and did not show photoinhibition at irradiances up to 796 μmol m⁻² s⁻¹. The specific growth rates of both Ceratium species were clearly decreased at L:D = 10:14 relative to those at L:D = 14:10 and L:D = 12:12. The present study indicates the two Ceratium species can adapt to a wide range of temperature and irradiance.     

Variation in huperzine A and B in Australasian Huperzia species

Huperzine A (HupA) and huperzine B (HupB) are alkaloids with acetylcholine esterase inhibitory activity and potential applications in the treatment of Alzheimer's disease. Both alkaloids were isolated in the 1980s from the Chinese lycopod Huperzia serrata (Thunb. ex Murray) Trevis., which has been used since the Tang dynasty as a traditional Chinese medicine. Most of the HupA currently used in herbal supplements and medicines worldwide is sourced from H. serrata which on average contains only 0.18 mg g⁻¹ dry wt HupA and is experiencing a rapid decline in China due to over-harvesting. Eleven Australasian Huperzia species were surveyed and nine species were found to contain both alkaloids, with a significant positive relationship observed between HupA and the lower abundance HupB. An Australian Huperzia carinata plant had one of the highest HupA concentrations recorded for a plant (1.03 mg g⁻¹ dry wt) and an Huperzia phlegmaria plant had the highest HupB value of all species surveyed (0.23 mg g⁻¹ dry wt). Intra-specific variation in huperzine concentration was examined for H. phlegmaria and Huperzia phlegmarioides and both HupA and HupB varied substantially within each species, but this variation was unrelated to foliar nitrogen levels.     

The routine metabolic rate of mulloway (Argyrosomus japonicus: Sciaenidae) and yellowtail kingfish (Seriola lalandi: Carangidae) acclimated to six different temperatures

This study compared the mass-specific routine metabolic rate (RMR) of similar sized mulloway (Argyrosomus japonicus), a sedentary species, and yellowtail kingfish (Seriola lalandi), a highly active species, acclimated at one of several temperatures ranging from 10–35 °C. Respirometry was carried out in an open-top static system and RMR corrected for seawater–atmosphere O₂ exchange using mass-balance equations. For both species RMR increased linearly with increasing temperature (T). RMR for mulloway was 5.78T − 29.0 mg O₂ kg^− 0.8 h^− 1 and for yellowtail kingfish was 12.11T − 39.40 mg O₂ kg^− 0.8 h^− 1. The factorial difference in RMR between mulloway and yellowtail kingfish ranged from 2.8 to 2.2 depending on temperature. The energetic cost of routine activity can be described as a function of temperature for mulloway as 1.93T − 9.68 kJ kg^− 0.8 day^− 1 and for yellowtail kingfish as 4.04T − 13.14 kJ kg^− 0.8 day^− 1. Over the full range of temperatures tested Q₁₀ values were approximately 2 for both species while Q₁₀ responses at each temperature increment varied considerably with mulloway and yellowtail kingfish displaying thermosensitivities indicative of each species respective niche habitat. RMR for mulloway was least thermally dependent at 28.5 °C and for yellowtail kingfish at 22.8 °C. Activation energies (E_a) calculated from Arrhenius plots were not significantly different between mulloway (47.6 kJ mol^− 1) and yellowtail kingfish (44.1 kJ mol^− 1).     

The effect of seasonality on oxidative metabolism in Nacella (Patinigera) magellanica

We studied the seasonal variation on aerobic metabolism and the response of oxidative stress parameters in the digestive glands of the subpolar limpet Nacella (P.) magellanica. Sampling was carried out from July (winter) 2002 to July 2003 in Beagle Channel, Tierra del Fuego, Argentina. Whole animal respiration rates increased in early spring as the animals spawned and remained elevated throughout summer and fall (winter: 0.09 ± 0.02 μmol O₂ h^− 1 g^− 1; summer: 0.31 ± 0.06 μmol O₂ h^− 1 g^− 1). Oxidative stress was assessed at the hydrophilic level as the ascorbyl radical content / ascorbate content ratio (A / AH⁻). The A / AH⁻ ratio showed minimum values in winter (3.7 ± 0.2 10^− 5 AU) and increased in summer (18 ± 5 10^− 5 AU). A similar pattern was observed for lipid radical content (122 ± 29 pmol mg^− 1 fresh mass [FW] in winter and 314 ± 45 pmol mg^− 1 FW in summer), iron content (0.99 ± 0.07 and 2.7 ± 0.6 nmol mg^− 1 FW in winter and summer, respectively) and catalase activity (2.9 ± 0.2 and 7 ± 1 U mg^− 1 FW in winter and summer, respectively). Since nitrogen derived radicals are thought to be critically involved in oxidative metabolism in cells, nitric oxide content was measured and a significant difference in the content of the Fe–MGD–NO adduct in digestive glands from winter and summer animals was observed. Together, the data indicate that both oxygen and nitrogen radical generation rates in N. (P.) magellanica are strongly dependent on season.     

Interactions between Prorocentrum donghaiense Lu and Scrippsiella trochoidea (Stein) Loeblich III under laboratory culture

Interactions between Prorocentrum donghaiense Lu and Scrippsiella trochoidea (Stein) Loeblich III, two species of causative bloom dinoflagellates in China, were investigated using bi-algal cultures under controlled laboratory conditions. The growth of P. donghaiense and S. trochoidea were significantly suppressed when the initial cell densities were set at 1.9 × 10⁴ cells mL⁻¹ or 1.9 × 10⁵ cells mL⁻¹ for P. donghaiense and 1.0 × 10⁴ cells mL⁻¹ for S. trochoidea when the initial size/density ratio was 1:1 or 10:1, respectively, but no out-competement was observed in either bi-algal culture by the end. The simultaneous assay on the culture filtrate showed that P. donghaiense filtrate prepared at a lower initial density (1.9 × 10⁴ cells mL⁻¹) stimulated the co-cultured S. trochoidea at a density of 1.0 × 10⁴ cells mL⁻¹, but filtrate at a higher density (1.9 × 10⁵ cells mL⁻¹) depressed its growth. Differently, the filtrate of S. trochoidea at a density of 1.0 × 10⁴ cells mL⁻¹ significantly suppressed the growth of P. donghaiense at a density of 1.9 × 10⁴ cells mL⁻¹, but had little stimulatory effect on P. donghaiense at a density of 1.9 × 10⁵ cells mL⁻¹compared to the control (P > 0.05). It is likely that these two species of microalgae interact with each other mainly by releasing allelochemical substance(s) into the culture medium, and a direct cell-to-cell contact was not necessary for their mutual interaction. We then quantify their interactions in the bi-algal culture by using a mathematical model. The estimated parameters from the model showed that the inhibition exerted by S. trochoidea on P. donghaiense was about 43 and 24 times stronger than the inhibitory effect that P. donghaiense exerted on S. trochoidea when the initial size/density were 1:1 and 10:1, respectively. S. trochoidea seemed to have a survival strategy that was superior to P. donghaiense in the bi-algal culture under controlled laboratory conditions. We also observed a closely positive relationship between the initial cell density and its effect on the co-cultured microalga by measuring the fluorenscence: filtrate prepared from higher initial cell density had stronger interference on the co-cultured microalga. Moreover, pre-treated under different temperature conditions (30 °C, 60 °C and 100 °C) would significantly changed the effect of culture filtrate on the co-cultured microalga. Result inferred that P. donghaiense or S. trochoidea would release allelochemicals into the bi-algal culture medium and the allelochemicals might be a mixture with temperature-sensitive components in it.     

Biodesulfurization of dibenzothiophene by a newly isolated Rhodococcus erythropolis strain

A new dibenzothiophene (DBT) desulfurizing bacterium was isolated from oil-contaminated soils in Iran. HPLC analysis and PCR-based detection of the presence of the DBT desulfurization genes (dszA, dszB and dszC) indicate that this strain converts DBT to 2-hydroxybiphenyl (2-HBP) via the 4S pathway. The strain, identified as Rhodococcus erythropolis SHT87, can utilize DBT, dibenzothiophene sulfone, thiophene, 2-methylthiophene and dimethylsulfoxide as a sole sulfur source for growth at 30 °C.The maximum specific desulfurization activity of strain SHT87 resting cells in aqueous and biphasic organic–aqueous systems at 30 °C was determined to be 0.36 and 0.47 μmol 2-HBP min⁻¹ (g dry cell)⁻¹, respectively. Three mM DBT was completely metabolized by SHT87 resting cells in the aqueous and biphasic systems within 10 h. The rate and the extent of the desulfurization reaction by strain SHT87 suggest that this strain can be used for the biodesulfurization of diesel oils.     

Diet and physiological responses of Spondyliosoma cantharus (Linnaeus, 1758) to the Caulerpa racemosa var. cylindracea invasion

Marine invasions are a worldwide problem that involves changes in communities and the acclimation of organisms to them. The invasive Chlorophyte Caulerpa racemosa var. cylindracea is widespread in the Mediterranean and colonises large areas from 0 to 70 m in depth. The omnivorous fish Spondyliosoma cantharus presents a high frequency of occurrence of C. racemosa in the stomach contents at invaded areas (76.3%) while no presence of C. racemosa was detected in control areas. The isotopic composition of muscle differed significantly between invaded and non-invaded sites for δ¹³C (− 16.67‰ ± 0.09 and − 17.67‰ ± 0.08, respectively), δ¹⁵N (10.22‰ ± 0.22 and 9.32‰ ± 0.18, respectively) and the C:N ratio (2.01 ± 0.0002 and 1.96 ± 0.009, respectively). Despite the high frequency of occurrence of C. racemosa in the stomach contents of S. cantharus and its important contribution to the δ¹³C source (20.7% ± 16.2), the contribution of C. racemosa to the δ¹⁵N in S. cantharus food sources was very low (6.6% ± 5.8). Other invertebrate prey such as decapods and polychaetes were more important contributors to the δ¹⁵N source at both invaded and non-invaded sites. Activation of enzymatic pathways (catalase, superoxide dismutase, glutathione-s-tranferase, 7-ethoxy resorufin O-de-ethylase) but not a significant increase in lipid peroxidation MDA (0.49 ± 0.01 nmol/mg prot at non-invaded and 0.53 ± 0.01 nmol/mg prot at invaded sites) was observed in S. cantharus individuals living in C. racemosa-invaded sites compared with control specimens. The low δ¹⁵N contribution values of C. racemosa by S. cantharus together with the toxicity demonstrated by the activation of the antioxidant defences and the important contribution of invertebrate prey to the δ¹⁵N could mean that the ingestion of C. racemosa by S. cantharus might be unintentional during the predation of invertebrate preys living underneath the entanglement of the C. racemosa fronds and stolons mats.     

Molecular mass and chain conformations of Rhizoma Panacis Japonici polysaccharides

The molecular mass and size of five water-soluble polysaccharides isolated from Rhizoma Panacis Japonici (RPJ) were determined with laser light scattering (LLS), size-exclusion chromatography (SEC) combined with LLS (SEC–LLS), dynamic light scattering (DLS), as well as transmission electron microscope (TEM). Their weight-average molecular masses (M_w) were 3.5 × 10⁴, 1.47 × 10⁵, 1.24 × 10⁶, 9.26 × 10⁵ and 1.36 × 10⁶, radii of gyration (<s²>_z^1/2) were 14.7, 31.7, 50.8, 41.8 and 40.4 nm, and hydrodynamic radii (R_h) were 19.9, 37.5, 66.2, 52.1, and 55.2 nm, respectively. The results showed that molecular masses and sizes of the polysaccharides were influenced by the pH and temperature of the extraction mediums. The conformation parameters were calculated from the above data according to polymer solution theory. The values of ρ (= <s²>_z^1/2/R_h) were from 0.7 to 0.8, exponents (ν) of <s²>_z^1/2 = k M_w^ν were from 0.31 to 0.43, and fractal dimension (d_f) were from 2.3 to 3.2, respectively. The results revealed that all of the polysaccharides existed as spheres in 0.15 M NaCl aqueous solution. TEM and atomic force microscope (AFM) further confirmed the spherical morphologies of these molecules. The spherical conformations of the polysaccharides were a result of their highly branched structures.     

Characterization, dynamics, and ecological impacts of harmful Cochlodinium polykrikoides blooms on eastern Long Island, NY, USA

We report on the emergence of Cochlodinium polykrikoides blooms in the Peconic Estuary and Shinnecock Bay, NY, USA, during 2002–2006. Blooms occurred during late summer when temperatures and salinities ranged from 20 to 25 °C and 22 to 30 ppt, respectively. Bloom patches achieved cell densities exceeding 10⁵ ml⁻¹ and chlorophyll a levels exceeding 100 μg l⁻¹, while background bloom densities were typically 10³–10⁴ cells ml⁻¹. Light, scanning electron and ultrathin-section transmission electron microscopy suggested that cells isolated from blooms displayed characteristics of C. polykrikoides and provide the first clear documentation of the fine structure for this species. Sequencing of a hypervariable region of the large subunit rDNA confirmed this finding, displaying 100% similarity to other North American C. polykrikoides strains, but a lower similarity to strains from Southeast Asia (88–90%). Bioassay experiments demonstrated that 24 h exposure to bloom waters (>5 × 10⁴ cells ml⁻¹) killed 100% of multiple fish species (1-week-old Cyprinodon variegates, adult Fundulus majalis, adult Menidia menidia) and 80% of adult Fundulus heteroclitus. Microscopic evaluation of the gills of moribund fish revealed epithelial proliferation with focal areas of fusion of gill lamellae, suggesting impairment of gill function (e.g. respiration, nitrogen excretion, ion balance). Lower fish mortality was observed at intermediate C. polykrikoides densities (10³–10⁴ cells ml⁻¹), while fish survived for 48 h at cell densities below 1 × 10³ cells ml⁻¹. The inability of frozen and thawed-, or filtered (0.2 μm)-bloom water to cause fish mortality suggested that the thick polysaccharide layer associated with cell membranes and/or a toxin principle within this layer may be responsible for fish mortality. Juvenile bay scallops (Argopecten irradians) and American oysters (Crassostrea virginica) experienced elevated mortality compared to control treatments during a 9-day exposure to bloom water (5 × 10⁴ cells ml⁻¹). Surviving scallops exposed to bloom water also experienced significantly reduced growth rates. Moribund shellfish displayed hyperplasia, hemorrhaging, squamation, and apoptosis in gill and digestive tissues with gill inflammation specifically associated with areas containing C. polykrikoides cells. In summary, our results indicate C. polykrikoides blooms have become annual events on eastern Long Island and that bloom waters are capable of causing rapid mortality in multiple species of finfish and shellfish.     

Candida chanthaburiensis sp. nov., Candida kungkrabaensis sp. nov. and Candida suratensis sp. nov., three novel yeast species from decaying plant materials submerged in water of mangrove forests

In a taxonomic study of yeasts isolated from decaying plant materials submerged in water of mangrove forests in Thailand, three strains isolated from tree bark (EM33^T), a fallen leaf (EM40^T) and a detached branch (SM56^T) were found to represent three novel yeast species. On the basis of morphological, biochemical, physiological and chemotaxonomic characteristics, the sequence analysis of the D1/D2 domain of the large subunit (LSU) rRNA gene, and the phylogenetic analysis, the three strains were assigned as three novel Candida species. They were named as Candida chanthaburiensis sp. nov. (type strain EM33^T = BCC 23057^T = NBRC 102176^T = CBS 10926^T), Candida kungkrabaensis sp. nov. (type strain EM40^T = BCC 23060^T = NBRC 102179^T = CBS 10927^T), and Candida suratensis sp. nov. (type strain SM56^T = BCC 25961^T = NBRC 103858^T = CBS 10928^T).     

First occurrence of Cochlodinium blooms in Sabah, Malaysia

Harmful algal blooms (HABs) resulting in red discoloration of coastal waters in Sepanggar Bay, off Kota Kinabalu, Sabah, East Malaysia, were first observed in January 2005. The species responsible for the bloom, which was identified as Cochlodinium polykrikoides, coincided with fish mortalities in cage-cultures. Determinations of cell density between January 2005 and June 2006 showed two peaks that occurred in March–June 2005 and June 2006. Cell abundance reached a maximum value of 6 × 10⁶ cells L⁻¹ at the fish cage sampling station where the water quality was characterized by high NO₃–N and PO₄–P concentrations. These blooms persisted into August 2005, were not detected during the north–east monsoon season and occurred again in May 2006. Favorable temperature, salinity and nutrient concentrations, which were similar to those associated with other C. polykrikoides blooms in the Asia Pacific region, likely promoted the growth of this species. Identification of C. polykrikoides as the causative organism was based on light and scanning microscopy, and confirmed by partial 18S ribosomal DNA sequences of two strains isolated during the bloom event (GenBank accession numbers DQ915169 and DQ915170).     

Relationship between the aerobic and anaerobic metabolic capacities and the vertical distribution of three intertidal sessile invertebrates: Jehlius cirratus(Darwin) (Cirripedia), Perumytilus purpuratus (Lamarck) (Bivalvia) and Mytilus chilensis (Hupé) (Bivalvia)

In protected areas of the southern Chilean coastline, the barnacle Jehlius cirratus dominates the upper intertidal zone, the bivalve Perumytilus purpuratus is the dominating species in the intermediate zone and Mytilus chilensis in the middle-lower zone. Varying degrees of aerial respiration were observed in the laboratory for these three sessile invertebrates: 80–100% of the immersed oxygen uptake for Jehlius cirratus, 30–50% for Perumytilus purpuratus and 5–15% for Mytilus chilensis. The pyruvate kinase/phosphoenolpyruvate carboxykinase (PK/PEPCK) ratio (adductor muscle) was higher for P. purpuratus than for M. chilensis. J. cirratus had no PEPCK activity in total soft tissues, under the assay conditions used in this study, and PK activity was higher for the cirriped than that of both bivalves. Succinate was produced in both mussels when exposed to hypoxic conditions, but it was not detected in J. cirratus. The kinetic parameters of the PK revealed that M. chilensis presented the highest _0.5 value for PEP and J. cirratus the lowest. Alanine inhibited the PK from M. chilensis to a greater extent (higher n_H value) and did not affect the PK of the cirriped. This latter enzyme also presented a marked substrate inhibition, above PEP concentrations of 0.5 mM. The evidence suggests that organisms inhabiting the upper intertidal zone could utilize an aerobic metabolism, given their high aerial respiration capacity, and that the succinate anaerobic pathway could be a more important metabolic strategy in species of the middle-lower intertidal zone. The physiological and biochemical capacities of these three species could thus be correlated with their vertical distribution in the intertidal rocky shore.     

Characterization of a root-specific β-thioglucoside glucohydrolase gene in Carica papaya and its recombinant protein expressed in Pichia pastoris

Plant β-thioglucoside glucohydrolases (TGGs or myrosinases) are a young class of enzymes in the glycosyl hydrolase family 1 and have a narrow distribution. TGG genes have mainly been cloned from crucifers, while TGGs in other species have received little attention. The TGG gene CpTGG2 and its recombinant protein from papaya were characterized in this paper. This is the first plant TGG gene without unusual intron splicing borders, as present in all other available TGG genes. Phylogenetic analysis indicated that plant myrosinases are divided into two major lineages. CpTGG2 is located in the lineage constituted by AtTGG4–6 from Arabidopsis thaliana, while the rest of myrosinases (including MA, MB and MC subfamilies) are grouped into another lineage. RT-PCR analysis indicated that CpTGG2 was specifically expressed in the root. The recombinant CpTGG2 expressed in yeast had a subunit mass of 70 kDa, and had low basal TGG activity without addition of ascorbate. Low concentrations of ascorbate stimulated CpTGG2 activity, while high concentrations were inhibitory. CpTGG2 was active in broad pH and temperature ranges, similar to AtTGG4 and AtTGG5. The apparent K_m and V_max were 2.24 mM and 24.3 μmol min⁻¹ mg⁻¹ when sinigrin was the substrate. The calculated k_cat/K_m value was 1.3 × 10⁴ S⁻¹ M⁻¹_. Our results reshaped and expanded the myrosinase family structure and provided clues to the evolution of myrosinase genes.     

High-level expression of recombinant phospholipase C from Bacillus cereus in Pichia pastoris and its characterization

The phospholipase c (plc) gene from Bacillus cereus was cloned into the pPICZC vector and integrated into the genome of Pichia pastoris. The phospholipase C (PLC) when expressed in P. pastoris was fused to the -factor secretion signal peptide of Saccharomyces cerevisiae and secreted into a culture medium. Recombinant P. pastoris X-33 had a clear PLC band at 28.5 kDa and produced an extracellular PLC with an activity of 678 U mg^–1 protein which was more than a recombinant P. pastoris GS115 (552 U mg^–1 protein) or KM71H (539 U mg^–1 protein). The PLCs were purified using a HiTrap affinity column with a specific activity of 1335 U mg^–1 protein by P. pastoris GS115, 1176 U mg^–1 protein by P. pastoris KM71H and 1522 U mg^–1 protein by P. pastoris X-33. The three recombinant PLCs had high PLC activity in the low pH range of 4-5 and higher thermal stability (e.g. stable at 75 °C) than the wild-type PLC from B. cereus. Some organic solvents, surfactants and metal ions, e.g. methanol, acetone, Co²⁺ and Mn²⁺ etc., also influenced the activity of the recombinant PLCs.     

Physiological acclimation to light in Chara intermedia nodes

In this study we investigated the ability of Chara intermedia to acclimate to different irradiances (i.e. “low-light” (LL): 20–30 μmol photons m⁻² s⁻¹ and “high-light” (HL): 180–200 μmol photons m⁻² s⁻¹) and light qualities (white, yellow and green), using morphological, photosynthesis, chlorophyll fluorescence and pigment analysis.Relative growth rates increased with increasing irradiance from 0.016 ± 0.003 (LL) to 0.024 ± 0.005 (HL) g g⁻¹ d⁻¹ fresh weight and were independent of light quality. A growth-based branch orientation towards high-light functioning as a mechanism to protect the plant from excessive light was confirmed. It was shown that the receptor responsible for the morphological reaction is sensitive to blue-light.C. intermedia showed higher oxygen evolution (up to 10.5 (HL) vs. 4.5 (LL) nmol O₂ mg Chl⁻¹ s⁻¹), photochemical and energy-dependent Chl fluorescence quenching and a lower Fv/Fm after acclimation to HL. With respect to qP, the acclimation of the photosynthetic apparatus depended on light quality and needed the blue part of the spectrum for full development. In addition, pigment composition was influenced by light and the Chl a/Car and Antheraxanthin (A) + Zeaxanthin (Z)/Violaxanthin (V) + A + Z (DES) ratios revealed the expected acclimation behaviour in favour of carotenoid protection under HL (i.e. decrease of Chl a/Car from 3.41 ± 0.48 to 2.30 ± 0.35 and increase of DES from 0.39 ± 0.05 to 0.87 ± 0.03), while the Chl a/Chl b ratios were not significantly affected. Furthermore it was shown that morphological light acclimation mechanisms influence the extent of the physiological modifications.     

Isolation of cobalt hyper-resistant mutants of Saccharomyces cerevisiae by in vivo evolutionary engineering approach

Cobalt is an important element with magnetic properties used in various industrial applications, but is also needed for biological activity. Very little is known about the cellular response of living systems to cobalt stress. Towards investigating this mechanism, we isolated individual Saccharomyces cerevisiae cells resistant to high cobalt concentrations up to 8 mmol l⁻¹, by employing four different ‘in vivo’ evolutionary engineering strategies: selection under constant or gradually increasing stress levels, and selection under continuous or pulse exposure to cobalt stress. Selection under continuous exposure to gradually increasing cobalt stress levels yielded the most resistant cell population to cobalt. However, the resistance was highly heterogeneous within the mutant populations ranging from 3- to 3700-fold survival rate of isolated individuals to 8 mmol l⁻¹ CoCl₂ in the most resistant population. Moreover, cobalt-resistant individual colonies were associated with 2–4-times lower intracellular cobalt contents as compared to wild-type, and with cross-resistance to metals such as nickel, zinc, manganese, but not to copper and chromium ions. Contrary to mutants evolved under continuous exposure to cobalt, those isolated by pulse exposure strategy also exhibited resistance to heat shock and hydrogen peroxide stress. Taken together, this study reinforced the fact that evolutionary engineering is useful in selecting strains with very specific phenotypes, and further illustrated the importance of the strategy chosen to isolate the best evolved strain.     

In planta selfing and oospore production of Phytophthora cinnamomi in the presence of Acacia pulchella

This paper provides the first evidence of A2 type 1 and type 2 isolates of Phytophthora cinnamomi producing selfed oospores in planta in an Australian soil and in a potting mix. Oospores were observed in infected lupin (Lupinus angustifolius) roots incubated for 7 d either in the substrate under potted Acacia pulchella plants, or in soils collected from under and near varieties of A. pulchella in jarrah (Eucalyptus marginata) forest. The A2 type isolates varied in their ability to produce selfed oospores and none were produced by A1 isolates. The gametangial association was amphigynous and spores were predominantly spherical with diameters from 13–40 μm. The oospores were viable but dormant. Two A2 type isolates produced small numbers of selfed oospores with amphigynous antheridia axenically in Ribeiro's liquid medium within 30 d, and one A2 type 2 isolate produced oospores after mating with an A1 strain. Evidence is presented that the presence of roots of Acacia pulchella, and particularly A. pulchella var. glaberrima and var. goadbyi, enhances the production of oospores.     

Thermoregulation of water foraging wasps (Vespula vulgaris and Polistes dominulus)

A comparison of the thermoregulation of water foraging wasps (Vespula vulgaris, Polistes dominulus) under special consideration of ambient temperature and solar radiation was conducted. The body surface temperature of living and dead wasps was measured by infrared thermography under natural conditions in their environment without disturbing the insects’ behaviour. The body temperature of both of them was positively correlated with T_a and solar radiation. At moderate T_a (22–28 °C) the regression lines revealed mean thorax temperatures (T_th) of 35.5–37.5 °C in Vespula, and of 28.6–33.7 °C in Polistes. At high T_a (30–39 °C) T_th was 37.2–40.6 °C in Vespula and 37.0–40.8 °C in Polistes. The thorax temperature excess (T_th–T_a) increased at moderate T_a by 1.9 °C (Vespula) and 4.4 °C (Polistes) per kW⁻¹ m⁻². At high T_a it increased by 4.0 °C per kW⁻¹ m⁻² in both wasps. A comparison of the living water foraging Vespula and Polistes with dead wasps revealed a great difference in their thermoregulatory behaviour. At moderate T_a (22–28 °C) Vespula exhibited distinct endothermy in contrast to Polistes, which showed only a weak endothermic activity. At high T_a (30–39 °C) Vespula reduced their active heat production, and Polistes were always ectothermic. Both species exhibited an increasing cooling effort with increasing insolation and ambient temperature.     

Selection of Beauveria bassiana isolates for control of the whiteflies Bemisia tabaci and Trialeurodes vaporariorum on the basis of their virulence, thermal requirements, and toxicogenic activity

As part of a 3-fold approach to select potential mycoinsecticides for whitefly control, we evaluated infectivity, thermal requirements, and toxicogenic activity of the entomopathogenic fungus Beauveria bassiana (Ascomycota: Clavicipitaceae) under laboratory conditions. Twenty-five native B. bassiana isolates and a commercially available mycoinsecticide (based on B. bassiana) were evaluated for virulence to fourth instar nymphs of sweetpotato whitefly, Bemisia tabaci, and greenhouse whitefly, Trialeurodes vaporariorum, at a concentration of 1 × 10⁷ conidia/ml. All isolates were pathogenic for both whitefly species, whereas mortality rates varied from 3 to 85%. A second series of bioassays was conducted on 10 selected isolates using four 10-fold concentrations ranging from 1 × 10⁵ to 1 × 10⁸ conidia/ml. Median lethal concentrations (LC₅₀) of the four most virulent isolates varied from 1.1 × 10⁵ to 6.2 × 10⁶ conidia/ml and average survival time (AST) of treated nymphs from 5.9 to 7.4 days. T. vaporariorum were significantly more susceptible to all B. bassiana isolates than B. tabaci. The thermal biology of the eight most virulent isolates to both whitefly species was investigated at six temperatures (10–35 °C). The colony radial growth rate was estimated from the slope of the linear regression of colony radius on time and data were then fitted to a modified generalized β function that accounted for 90.5–99.3% of the data variance. Optimum temperatures for extension rate ranged from 23.1 to 27.1 °C, whereas maximum temperatures for fungal growth varied from 31.8 to 36.6 °C. On the basis of their virulence and thermal requirements, three isolates showed promise as candidates for whitefly management in Mediterranean greenhouses. Whilst in vitro production of macromolecular compounds toxic to Galleria mellonella larvae was not a requisite for virulence, ASTs of larvae injected with Sephadex G-25 fractions from candidate isolates ranged from 1.4 to 3.7 days compared with 5–6 days for non-toxic G-25 fractions. In addition, proteinase K treatment significantly reduced their toxic activity suggesting that they were proteins and revealing the potential of these isolates to be further improved through biotechnology to kill the pest more quickly.