A new in vivo fluorimetric technique to measure growth of adhering phototrophic microorganisms

193

133

Section: Discussionmentioning

confidence: 99%

NONDESTRUCTIVE TRACING OF MIGRATORY RHYTHMS OF INTERTIDAL BENTHIC MICROALGAE USING IN VIVO CHLOROPHYLL A FLUORESCENCE^1,²

Serôdio

Silva

Catarino

1997

193

133

“…Before measuring growth rates, cultures were preconditioned to each salinity used in the experiments to avoid kinetics of stress and recovery after osmotic shocks. Growth experiments were carried out in (Karsten et al 1996). Measurements were taken at the same time of the day on dilute cultures only to avoid the progressive decrease in growth rate that sets in with shelf shading and the strong decrease in fluorescence per cell typical of nutrient-limited cultures.…”

Section: Methodsmentioning

confidence: 99%

Salinity Tolerance of Diatoms From Thalassic Hypersaline Environments

Clavero

Hernández-Mariné

Grimalt

et al. 2000

Thirty‐four benthic diatom strains were isolated from thalassic hypersaline marine environments and their salinity tolerance characterized in growth experiments conducted at salinities ranging from 0.5% to 17.5% (weight of total salts per volume, g·100 mL−1). The results were compared with the patterns of diatom species distribution and abundance in hypersaline evaporation ponds and tidal channels of Guerrero Negro, Baja California Sur, Mexico. The isolated strains were representative of the diatom assemblages present in the saltern ponds but were less so of natural assemblages in tidal channels. In general, we found a clear decreasing trend of diatom diversity in the field and in the isolated strains with increasing salinity. With some exceptions, the upper limit of salinity tolerance in cultivated strains corresponded to their distribution in field samples. However, the relative abundance of species in the field was not correlated with growth rates achieved in culture for the same salinities. Most cultured strains exhibited extreme euryhalinity growing well from brackish to hypersaline conditions, but the particulars of salt tolerance were quite diverse among strains. The most halotolerant taxa, two Amphora species, Amphora cf. subacutiuscula Schoeman, Nitzschia fusiformis Grunow, and Entomoneis sp., grew well in salinities ranging from 0.5% to 15%. Three strains of Pleurosigma strigosum W. Smith that were unable to grow in salinities less than 5% total salts represent the only true halophilic diatoms ever reported. The fact that many strains displayed a remarkable halotolerance, with optimal or near‐optimal growth rates at salinities as high as three times that of seawater, implies that diatoms from hypersaline environments are evolutionarily highly adapted to such environments.

“…Increases in the in vivo chlorophyll a fluorescence of the cyanobacteria were recorded over time using a fluorimeter developed to measure growth of benthic phototrophic microorganisms. T h e fluorimeter is based on modulated excitation of blue light-emitting diodes with a photodiode as detector and is described in detail in Karsten et al (1996).…”

Section: Strains Of Microcoleus Chthonoplastes Thuret With the Locatimentioning

confidence: 99%

GROWTH AND ORGANIC OSMOLYTES OF GEOGRAPHICALLY DIFFERENT ISOLATES OF MICROCOLEUS CHTHONOPLASTES (CYANOBACTERIA) FROM BENTHIC MICROBIAL MATS:RESPONSE TO SALINITY CHANGE¹

Karsten

1996

The comparative growth and osmotic acclimation often culture strains of the marine benthic cyanobacterium Microcoleus chthonoplastes Thuret isolated from microbial mats in Germany, Spain, Egypt, the United States, Mexico, Chile, and Australia were investigated in salinities ranging from freshwater to twice seawater. All isolates showed a broad growth versus salinity response consistent with the dominance of this species in intertidal and hypersaline microbial communities. Growth optima, salinity preferences, and maximum growth rates differed for each isolate and could be related to the habitat from which they were isolated. This is most obvious when comparing strains from brackish habitats with those from a hypersaline lake. While the former isolates exhibited sharply pronounced growth optima under hyposaline conditions, cultures from the hypersaline environment grew best in salinity more than double seawater. The major low‐molecular weight organic compounds present in all M. chthonoplastes strains were the carbohydrates glycosylglycerol and trehalose. This was proven by using 13C‐nuclear magnetic resonance spectroscopy. Glycosylglycerol was synthesized and accumulated with increasing salinities, indicating its role as an osmolyte. In contrast, trehalose was present in relatively high concentrations under hyposaline conditions only. Differences in the patterns of growth versus salinity, as well as in those of osmotic acclimation among the M. chthonoplastes isolates, point to the development of different physiological ecotypes within the species.