scholarly journals Effects of Light Intensity and Exposure Period on the Growth and Stress Responses of Two Cyanobacteria Species: Pseudanabaena galeata and Microcystis aeruginosa

Water ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 407 ◽  
Author(s):  
Guligena Muhetaer ◽  
Takashi Asaeda ◽  
Senavirathna M. D. H. Jayasanka ◽  
Mahendra B. Baniya ◽  
Helayaye D. L. Abeynayaka ◽  
...  
Keyword(s):  
Microcystis Aeruginosa ◽  
Stress Responses ◽  
Exposure Period ◽  
Chl A ◽  
Light Levels ◽  
Light Intensities ◽  
Information Gap ◽  
Antioxidative Enzyme Activities ◽  
Species Specific ◽  
Pseudanabaena Galeata

Light is an important factor that affects cyanobacterial growth and changes in light can influence their growth and physiology. However, an information gap exists regarding light-induced oxidative stress and the species-specific behavior of cyanobacteria under various light levels. This study was conducted to evaluate the comparative effects of different light intensities on the growth and stress responses of two cyanobacteria species, Pseudanabaena galeata (strain NIES 512) and Microcystis aeruginosa (strain NIES 111), after periods of two and eight days. The cyanobacterial cultures were grown under the following different light intensities: 0, 10, 30, 50, 100, 300, and 600 μmol m−2 s−1. The optical density (OD730), chlorophyll a (Chl-a) content, protein content, H2O2 content, and the antioxidative enzyme activities of catalase (CAT) and peroxidase (POD) were measured separately in each cyanobacteria species. P. galeata was negatively affected by light intensities lower than 30 μmol m−2 s−1 and higher than 50 μmol m−2 s−1. A range of 30 to 50 μmol m−2 s−1 light was favorable for the growth of P. galeata, whereas M. aeruginosa had a higher tolerance for extreme light conditions. The favorable range for M. aeruginosa was 10 to 100 μmol m−2 s−1.

Pycnidium production by Botryodiplodia theobromae. I. The relation of light to the induction of pycnidia

1969 ◽  
Vol 47 (7) ◽  
pp. 1153-1156 ◽  
Author(s):  
J. A. Ekundayo ◽  
R. H. Haskins
Keyword(s):  
Light Intensity ◽  
Ultraviolet Radiation ◽  
Exposure Period ◽  
Fluorescent Light ◽  
Botryodiplodia Theobromae ◽  
Continuous Irradiation ◽  
Long Wave ◽  
Light Intensities ◽  
Glass Color ◽  
Color Filters

Cultures of Botryodiplodia theobromae Pat. produced pycnidia abundantly on several media under continuous irradiation with fluorescent light. The fungus did not sporulate when grown in darkness. Irradiation of cultures with a light intensity of 15 foot-candles for 4 days was sufficient to stimulate pycnidial production, but for appreciable sporulation to occur over the same exposure period, higher light intensities are required. Irradiation of cultures through glass color filters showed that long-wave ultraviolet radiation stimulated sporulation.

scholarly journals Using a two-layered sphere model to investigate the impact of gas vacuoles on the inherent optical properties of <i>Microcystis aeruginosa</i>

2013 ◽  
Vol 10 (12) ◽  
pp. 8139-8157 ◽  
Author(s):  
M. W. Matthews ◽  
S. Bernard
Keyword(s):  
Optical Properties ◽  
Microcystis Aeruginosa ◽  
Cyanobacterial Blooms ◽  
Shell Layer ◽  
Sphere Model ◽  
Homogeneous Population ◽  
Chl A ◽  
Inherent Optical Properties ◽  
Gas Vacuoles ◽  
The Impact

Abstract. A two-layered sphere model is used to investigate the impact of gas vacuoles on the inherent optical properties (IOPs) of the cyanophyte Microcystis aeruginosa. Enclosing a vacuole-like particle within a chromatoplasm shell layer significantly altered spectral scattering and increased backscattering. The two-layered sphere model reproduced features in the spectral attenuation and volume scattering function (VSF) that have previously been attributed to gas vacuoles. This suggests the model is good at least as a first approximation for investigating how gas vacuoles alter the IOPs. Measured Rrs was used to provide a range of values for the central value of the real refractive index, 1 + ε, for the shell layer using measured IOPs and a radiative transfer model. Sufficient optical closure was obtained for 1 + ε between 1.1 and 1.14, which had corresponding Chl a-specific phytoplankton backscattering, bbφ*, between 3.9 and 7.2 × 10−3 m2 mg−1 at 510 nm. The bbφ* values are in close agreement with the literature and in situ particulate backscattering measurements. Rrs simulated for a population of vacuolate cells was greatly enlarged relative to a homogeneous population. A sensitivity analysis of empirical algorithms for estimating Chl a in eutrophic/hypertrophic waters suggests these are robust under variable constituent concentrations and likely to be species-sensitive. The study confirms that gas vacuoles cause significant increase in backscattering and are responsible for the high Rrs values observed in buoyant cyanobacterial blooms. Gas vacuoles are therefore one of the most important bio-optical substructures influencing the IOPs in phytoplankton.

scholarly journals Effect of Zinc on Microcystis aeruginosa UTEX LB 2385 and Its Toxin Production

Toxins ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 92 ◽  
Author(s):  
Jose L. Perez ◽  
Tinchun Chu
Keyword(s):  
Flow Cytometry ◽  
Stress Response ◽  
Microcystis Aeruginosa ◽  
Stress Responses ◽  
Algal Blooms ◽  
Phase Contrast ◽  
Phase Contrast Microscopy ◽  
Zinc Stress ◽  
Cell Quota ◽  
Contrast Microscopy

Cyanobacteria harmful algal blooms (CHABs) are primarily caused by man-made eutrophication and increasing climate-change conditions. The presence of heavy metal runoff in affected water systems may result in CHABs alteration to their ecological interactions. Certain CHABs produce by-products, such as microcystin (MC) cyanotoxins, that have detrimentally affected humans through contact via recreation activities within implicated water bodies, directly drinking contaminated water, ingesting biomagnified cyanotoxins in seafood, and/or contact through miscellaneous water treatment. Metallothionein (MT) is a small, metal-sequestration cysteine rich protein often upregulated within the stress response mechanism. This study focused on zinc metal resistance and stress response in a toxigenic cyanobacterium, Microcystis aeruginosa UTEX LB 2385, by monitoring cells with (0, 0.1, 0.25, and 0.5 mg/L) ZnCl2 treatment. Flow cytometry and phase contrast microscopy were used to evaluate physiological responses in cultures. Molecular assays and an immunosorbent assay were used to characterize the expression of MT and MC under zinc stress. The results showed that the half maximal inhibitory concentration (IC50) was 0.25 mg/L ZnCl2. Flow cytometry and phase contrast microscopy showed morphological changes occurred in cultures exposed to 0.25 and 0.5 mg/L ZnCl2. Quantitative PCR (qPCR) analysis of selected cDNA samples showed significant upregulation of Mmt through all time points, significant upregulation of mcyC at a later time point. ELISA MC-LR analysis showed extracellular MC-LR (µg/L) and intracellular MC-LR (µg/cell) quota measurements persisted through 15 days, although 0.25 mg/L ZnCl2 treatment produced half the normal cell biomass and 0.5 mg/L treatment largely inhibited growth. The 0.25 and 0.5 mg/L ZnCl2 treated cells demonstrated a ~40% and 33% increase of extracellular MC-LR(µg/L) equivalents, respectively, as early as Day 5 compared to control cells. The 0.5 mg/L ZnCl2 treated cells showed higher total MC-LR (µg/cell) quota yield by Day 8 than both 0 mg/L ZnCl2 control cells and 0.1 mg/L ZnCl2 treated cells, indicating release of MCs upon cell lysis. This study showed this Microcystis aeruginosa strain is able to survive in 0.25 mg/L ZnCl2 concentration. Certain morphological zinc stress responses and the upregulation of mt and mcy genes, as well as periodical increased extracellular MC-LR concentration with ZnCl2 treatment were observed.

scholarly journals A Comparison of Stage Conversion in the Coccidian Apicomplexans Toxoplasma gondii, Hammondia hammondi, and Neospora caninum

2020 ◽  
Vol 10 ◽  
Author(s):  
Sarah L. Sokol-Borrelli ◽  
Rachel S. Coombs ◽  
Jon P. Boyle
Keyword(s):  
Life Cycle ◽  
Toxoplasma Gondii ◽  
Stress Responses ◽  
Neospora Caninum ◽  
Life Forms ◽  
New Host ◽  
Environmental Signals ◽  
Stage Conversion ◽  
Genetic Components ◽  
Species Specific

Stage conversion is a critical life cycle feature for several Apicomplexan parasites as the ability to switch between life forms is critical for replication, dissemination, pathogenesis and ultimately, transmission to a new host. In order for these developmental transitions to occur, the parasite must first sense changes in their environment, such as the presence of stressors or other environmental signals, and then respond to these signals by initiating global alterations in gene expression. As our understanding of the genetic components required for stage conversion continues to broaden, we can better understand the conserved mechanisms for this process and unique components and their contribution to pathogenesis by comparing stage conversion in multiple closely related species. In this review, we will discuss what is currently known about the mechanisms driving stage conversion in Toxoplasma gondii and its closest relatives Hammondia hammondi and Neospora caninum. Work by us and others has shown that these species have some important differences in the way that they (1) progress through their life cycle and (2) respond to stage conversion initiating stressors. To provide a specific example of species-specific complexities associated with stage conversion, we will discuss our recent published and unpublished work comparing stress responses in T. gondii and H. hammondi.

scholarly journals Light Exposure during Days with Night, Outdoor, and Indoor Work

2019 ◽  
Vol 63 (6) ◽  
pp. 651-665 ◽  
Author(s):  
Stine Daugaard ◽  
Jakob Markvart ◽  
Jens Peter Bonde ◽  
Jens Christoffersen ◽  
Anne Helene Garde ◽  
...  
Keyword(s):  
Light Intensity ◽  
Light Exposure ◽  
Spectral Composition ◽  
Working Hours ◽  
Well Being ◽  
Outdoor Workers ◽  
Light Levels ◽  
Light Intensities ◽  
Treatment Of Depression ◽  
Night Shifts

Abstract Objective To assess light exposure during days with indoor, outdoor, and night work and days off work. Methods Light intensity was continuously recorded for 7 days across the year among indoor (n = 170), outdoor (n = 151), and night workers (n = 188) in Denmark (55–56°N) equipped with a personal light recorder. White light intensity, duration above 80, 1000, and 2500 lux, and proportion of red, green, and blue light was depicted by time of the day and season for work days and days off work. Results Indoor workers’ average light exposure only intermittently exceeded 1000 lux during daytime working hours in summer and never in winter. During daytime working hours, most outdoor workers exceeded 2500 lux in summer and 1000 lux in winter. Night workers spent on average 10–50 min &gt;80 lux when working night shifts. During days off work, indoor and night workers were exposed to higher light intensities than during work days and few differences were seen between indoor, outdoor, and night workers. The spectral composition of light was similar for indoor, outdoor, and night workers during days at and off work. Conclusion The night workers of this study were during night hours on average exposed for a limited time to light intensities expected to suppress melatonin. The indoor workers were exposed to light levels during daylight hours that may reduce general well-being and mood, especially in winter. Outdoor workers were during summer daylight hours exposed to light levels comparable to those used for the treatment of depression.

Seasonal photosynthetic performance of Nereocystis luetkeana

1984 ◽  
Vol 62 (4) ◽  
pp. 664-670 ◽  
Author(s):  
W. N. Wheeler ◽  
R. G. Smith ◽  
L. M. Srivastava
Keyword(s):  
Flux Density ◽  
Late Summer ◽  
Photosynthetic Performance ◽  
Initial Slope ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Photosynthetic Rates ◽  
Chl A ◽  
Light Intensities ◽  
Nereocystis Luetkeana

Pigment levels, photosynthetic performance, and tissue nitrogen levels of three age-class blade disks of Nereocystis luetkeana were followed over one complete and two partial growth seasons. Chlorophyll (chl) a, fucoxanthin, and chlorophyll c all showed high levels in fall–winter and low levels in late summer. The molar ratios also varied with much higher fucoxanthin: chl a and chl c: chl a ratios in early spring than in late summer–fall. Plots of maximum photosynthetic rates (Pmax) at saturating light intensities and initial slopes (α) derived from photosynthetic rates at subsaturating light intensities also showed seasonal variations, with maxima in August and September and minima in April. The saturating light irradiance, IR, also showed a maximum in late summer and a minimum in winter. Tissue nitrate levels were high in winter, declined to near zero levels in May–August, and increased again in fall–winter. Amino acids and total N followed a similar pattern. The older tissues farthest from the bulb had higher Pmax and pigment levels as well as internal nitrate levels than young proximal tissues. Environmental data on sea-water nitrate, photon flux density, and temperature and data on mannitol and total C are presented. It appears that there is a significant negative correlation between photon flux density and initial slope of photosynthesis and between Pmax and temperature below 15 °C. At temperatures above 15 °C, internal N concentrations, which in turn are governed by the ambient nitrate concentration, appear to become limiting. Pigment levels, especially chlorophyll a, showed a direct correlation with ambient nitrate. These data are discussed in relation to the possible biennial nature and growth strategy of Nereocystis.

scholarly journals RNA atlas of human bacterial pathogens uncovers stress dynamics linked to infection

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Kemal Avican ◽  
Jehad Aldahdooh ◽  
Matteo Togninalli ◽  
A. K. M. Firoj Mahmud ◽  
Jing Tang ◽  
...  
Keyword(s):  
Stress Responses ◽  
Large Scale ◽  
Bacterial Pathogens ◽  
Stress Conditions ◽  
Altered Expression ◽  
Online Resource ◽  
Species Specific ◽  
In Vitro Stress

AbstractBacterial processes necessary for adaption to stressful host environments are potential targets for new antimicrobials. Here, we report large-scale transcriptomic analyses of 32 human bacterial pathogens grown under 11 stress conditions mimicking human host environments. The potential relevance of the in vitro stress conditions and responses is supported by comparisons with available in vivo transcriptomes of clinically important pathogens. Calculation of a probability score enables comparative cross-microbial analyses of the stress responses, revealing common and unique regulatory responses to different stresses, as well as overlapping processes participating in different stress responses. We identify conserved and species-specific ‘universal stress responders’, that is, genes showing altered expression in multiple stress conditions. Non-coding RNAs are involved in a substantial proportion of the responses. The data are collected in a freely available, interactive online resource (PATHOgenex).

scholarly journals Effect of Light Intensity and Leaf Temperature on Photosynthesis and Transpiration in Wheat and Sorghum

1970 ◽  
Vol 23 (4) ◽  
pp. 775 ◽  
Author(s):  
RW Downes
Keyword(s):  
Carbon Dioxide ◽  
Water Use ◽  
Carbon Dioxide Concentration ◽  
Leaf Temperature ◽  
High Light ◽  
Intercellular Spaces ◽  
Concentration Difference ◽  
Light Levels ◽  
Light Intensities ◽  
Water Vapour Concentration

Wheat stomata offered less resistance to water and carbon dioxide diffusion than sorghum stomata at light intensities of 0�06 and 0�26 cal cm-2 min-i (400-700 nm) but resistances were comparable at 0�46 cal cm-2 min-i. Consequently, transpiration rates were higher in wheat than in sorghum, except at the high light levels, in leaf chamber experiments described here. Rates of photosynthesis were higher in sorghum than in wheat, with the greatest difference at high light levels. This resulted in a greater efficiency of dry matter production relative to water use in sorghum. Transpiration rate increased with increased temperature in both species. Photosynthesis was independent of temperature in wheat, and in sorghum under low light conditions, but otherwise photosynthesis increased with temperature in sorghum. In both species, efficiency of water use decreased as temperature increased at all light intensities. Water vapour concentration difference between the intercellular spaces and the air was comparable in wheat and sorghum and increased with temperature. The carbon dioxide concentration difference between air and intercellular spaces was substantially greater in sorghum than in wheat and increased with leaf temperature. Maximum values were obtained at the intermediate light level in sorghum.

Changes in the Transcriptome of Dry Leafy Spurge (Euphorbia esula) Seeds Imbibed at a Constant and Alternating Temperature

Weed Science ◽  
2012 ◽  
Vol 60 (1) ◽  
pp. 48-56 ◽  
Author(s):  
Michael E. Foley ◽  
Wun S. Chao ◽  
Münevver Doğramaci ◽  
David P. Horvath ◽  
James V. Anderson
Keyword(s):  
Stress Responses ◽  
Anaerobic Respiration ◽  
Reducing Power ◽  
Principal Component ◽  
Leafy Spurge ◽  
Specific Effects ◽  
Temperature Regimes ◽  
Stress Related Genes ◽  
Alternating Temperature ◽  
Species Specific

Leafy spurge seeds are responsive to alternating temperature rather than constant temperature for germination. Transcriptome changes of dry leafy spurge seeds and seeds imbibed for 1 and 3 d at 20 C constant (C) and 20 : 30 C alternating (A) temperature were determined by microarray analysis to examine temperature responsiveness. Principal component analysis revealed differences in the transcriptome of imbibed seeds based on the temperature regime. Computational methods in bioinformatics parsed the data into overrepresented AraCyc pathways and gene regulation subnetworks providing biological context to temperature responses. After 1 d of imbibition, the degradation of starch and sucrose leading to anaerobic respiration were common pathways at both temperature regimes. Several overrepresented pathways unique to 1 d A were associated with generation of energy, reducing power, and carbon substrates; several of these pathways remained overrepresented and up-regulated at 3 d A. At 1 d C, pathways for the phytohormones jasmonic acid and brassinosteroids were uniquely overrepresented. There was little similarity in overrepresented pathways at 1 d C between leafy spurge and arabidopsis seeds, indicating species-specific effects upon imbibition of dry seeds. Overrepresented gene subnetworks at 1 d and 3 d at both temperature regimes related to signaling processes and stress responses. A major overrepresented subnetwork unique to 1 d C related to photomorphogenesis via the E3 ubiquitin ligase COP1. At 1 d A, major overrepresented subnetworks involved circadian rhythm via LHY and TOC1 proteins and expression of stress-related genes such as DREB1A, which is subject to circadian regulation. Collectively, substantial differences were observed in the transcriptome of leafy spurge seeds imbibed under conditions that affect the capacity to germinate.

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