The Languages Spoken in the Water Body (or the Biological Role of Cyanobacterial Toxins)

Although intensification of toxic cyanobacterial blooms over the last decade is a matter of growing concern due to bloom impact on water quality, the biological role of most of the toxins produced is not known. In this critical review we focus primarily on the biological role of two toxins, microcystins and cylindrospermopsin, in inter- and intra-species communication and in nutrient acquisition. We examine the experimental evidence supporting some of the dogmas in the field and raise several open questions to be dealt with in future research. We do not discuss the health and environmental implications of toxin presence in the water body

Phylogenetic and functional marker genes to study ammonia-oxidizing microorganisms (AOM) in the environment

The oxidation of ammonia plays a significant role in the transformation of fixed nitrogen in the global nitrogen cycle. Autotrophic ammonia oxidation is known in three groups of microorganisms. Aerobic ammonia-oxidizing bacteria and archaea convert ammonia into nitrite during nitrification. Anaerobic ammonia-oxidizing bacteria (anammox) oxidize ammonia using nitrite as electron acceptor and producing atmospheric dinitrogen. The isolation and cultivation of all three groups in the laboratory are quite problematic due to their slow growth rates, poor growth yields, unpredictable lag phases, and sensitivity to certain organic compounds. Culture-independent approaches have contributed importantly to our understanding of the diversity and distribution of these microorganisms in the environment. In this review, we present an overview of approaches that have been used for the molecular study of ammonia oxidizers and discuss their application in different environment

Methane- and ammonia-oxidizing bacteria at the chemocline of Lake Kinneret (Israel)

The vertical distribution of methane- and ammonia-oxidizing bacteria (MOB and AOB, respectively), and the physicochemical conditions in the chemocline of Lake Kinneret (Israel) were studied at a resolution of 10 cm from 16.2 to 17.7 m depth. Profiles of the chemical parameters indicated decreasing concentrations of methane (from 22.4 to 0.11 µmol l–1) and ammonia (from 14.2 to 8.4 µmol l–1) towards the water surface and in close proximity to the chemocline. The disappearance of methane coincided with methane oxidation that could be corroborated throughout this layer with highest rates at 17.4 to 17.6 m. Disappearance of ammonia could not be linked to ammonia oxidation exclusively. The genes pmoA and the homologous amoA (coding for subunit α of the methane and ammonia monooxygenase, respectively) were amplified by PCR. The products were analyzed by terminal restriction fragment length polymorphism (T-RFLP) and sequencing of clone libraries. The results demonstrated that different MOB and AOB communities are established along the concentration gradient within the narrow layer of the metalimnetic chemocline. Changes in the intensity of the T-RFLP peaks and the frequency of different groups of alpha- and gammaproteobacterial MOB, and betaproteobacterial AOB, coincided with the concentration gradients of methane, ammonia, nitrate, and oxygen in the chemocline. This suggests that different communities of MOB, and to a lesser extent AOB, contribute to the formation of chemical gradients of their particular substrates in the chemoclin

Phylogenetic and functional marker genes to study ammonia-oxidizing microorganisms (AOM) in the environment

The oxidation of ammonia plays a significant role in the transformation of fixed nitrogen in the global nitrogen cycle. Autotrophic ammonia oxidation is known in three groups of microorganisms. Aerobic ammonia-oxidizing bacteria and archaea convert ammonia into nitrite during nitrification. Anaerobic ammonia-oxidizing bacteria (anammox) oxidize ammonia using nitrite as electron acceptor and producing atmospheric dinitrogen. The isolation and cultivation of all three groups in the laboratory are quite problematic due to their slow growth rates, poor growth yields, unpredictable lag phases, and sensitivity to certain organic compounds. Culture-independent approaches have contributed importantly to our understanding of the diversity and distribution of these microorganisms in the environment. In this review, we present an overview of approaches that have been used for the molecular study of ammonia oxidizers and discuss their application in different environments

Long-Term Changes in Cyanobacteria Populations in Lake Kinneret (Sea of Galilee), Israel: An Eco-Physiological Outlook

The long-term record of cyanobacteria abundance in Lake Kinneret (Sea of Galilee), Israel, demonstrates changes in cyanobacteria abundance and composition in the last five decades. New invasive species of the order Nostocales (Aphanizomenon ovalisporum and Cylindrospermopsis raciborskii) became part of the annual phytoplankton assemblage during summer-autumn. Concomitantly, bloom events of Microcystis sp. (Chroococcales) during winter-spring intensified. These changes in cyanobacteria pattern may be partly attributed to the management policy in Lake Kinneret’s vicinity and watershed aimed to reduce effluent discharge to the lake and partly to climate changes in the region; i.e., increased water column temperature, less wind and reduced precipitation. The gradual decrease in the concentration of total and dissolved phosphorus and total and dissolved nitrogen and an increase in alkalinity, pH and salinity, combined with the physiological features of cyanobacteria, probably contributed to the success of cyanobacteria. The data presented here indicate that the trend of the continuous decline of nutrients may not be sufficient to reduce and to control the abundance and proliferation of toxic and non-toxic cyanobacteria