Shimshon Belkin

Thermococcus litoralis sp. nov.: A new species of extremely thermophilic marine archaebacteria

We describe a new species, Thermococcus litoralis, which is different from the type species Thermococcus celer in molecular, morphological and physiological characteristics.

Biological denitrification of drinking water using newspaper

Microbial denitrification of drinking water was studied in laboratory columns packed with shredded newspapers. Newspaper served as the sole carbon and energy substrate as well as the only physical support for the microbial population. Complete removal of nitrate (100 mg 1−1) was readily achieved, without accumulation of nitrite. The treated water contained low dissolved organic carbon (4–10 mg 1−1). The cellulose-dependent denitrification process was sensitive to changes in temperature: nitrate removal rates at 14°C were approximately one third of the rates observed at 32°C. Pretreatment of newspaper with diluted NaOH or diluted HCl, or by autoclave did not improve the efficiency of the process. A time-dependent decay in denitrification rate was noticeable after several months of operation. The reasons for this phenomenon, which may be due to weakened adhesion of the bacteria to the substrate, are under investigation.

Thermotoga neapolitana sp. nov. of the extremely thermophilic, eubacterial genus Thermotoga

A second species of the extremely thermophilic, eubacterial genus Thermotoga is described as clearly distinguished from the type species Thermotoga maritima by physiological and phylogenetic criteria. It is named Thermotoga neapolitana.

Denitrification in laboratory sand columns: Carbon regime, gas accumulation and hydraulic properties

Microbiological denitrification in a sandy matrix was studied by means of laboratory sand columns operated at continuous and pulse feed regimes. Gas production resulting from the biological activity played a major role in modifying the hydraulic properties of the column, leading to decreases in hydraulic conductivity and porosity, higher water velocities through the column, higher dispersion and anomalies in the head difference to flow rates ratios. All of these effects were more pronounced when formate, the carbon source used, was supplied continuously: microbial activity and gas production were concentrated at the top of the column, leading to almost complete clogging. When the formate was supplied in pulses, activity and gas production were dispersed, leading to relative uniformity in the physical parameters measured and a homogeneous appearance of the column. The results suggest that in a futurein situ aquifer denitrification plant, pulse application of the carbon source is prefereable to a continuous supply regime.

High internal pH conveys ammonia resistance in spirulina platensis

Spirulina platensis is an alkalophilic cyanobacterium, often cultivated in mass cultures. Unlike many other photosynthetic microorganisms, it is capable of withstanding and even utilizing ammonia at high environmental pH. It is suggested that high internal pH values limit intracellular accumulation of ammonia, thus preventing uncoupling of photosynthesis. Furthermore, it is suggested that the high average internal pH (7.5) is conferred mainly by the intrathylakoid pH which is approximately 1 pH unit higher than in other cyanobacteria tested.

Monitoring subtoxic environmental hazards by stress‐responsive luminous bacteria

A novel approach to toxicant detection is described, based on monitoring bacterial reactions to environmental threats. In response to such stress, various defense mechanisms are turned on by initiating gene transcription at specific DNA sites known as promoters. To follow this transcription sensitively, such promoters were genetically fused in Escherichia coli to the lux (luminescence) genes from the bacterium Vibrio fischeri. The bacteria thus engineered now produce light in response to different environmental insults; this light is easy to measure and quantify. n n n nA wide range of promoters was utilized in this manner, to create over a dozen bacterial constructs that emit light in response to specific or general stress factors. The responses of four of these to defined chemicals and to wastewater samples are described. The threats reported by these bacteria include general and protein damage, DNA damage, and oxidative hazards (peroxides and oxygen radicals). Members of the tested panel exhibited very high sensitivity: generally, the luminescent response occurred at subtoxic doses of the stressing factor, and was evident within 20 min to 2 h after exposure. n n n nIt is proposed that these bacteria, or others constructed in a similar manner, can serve as powerful early-warning indicators of environmental pollution, as well as monitoring tools for the operation of different industrial processes, from fermentation reactors to wastewater treatment plants.

Biodegradation of haloalkanes

Halogenated alkanes constitute a significant group among the organic pollutants of environmental concern. Their industrial and agricultural uses are extensive, but until 1978 they were considered to be non-biodegradable. In recent years, microorganisms were described that could degrade, partially or fully, singly or in consortia, many of the compounds tested. The first step in haloalkane degradation appears to be universal: removal of the halogen atom(s). This is mediated by a group of enzymes, generally known as dehalogenases, acting in most cases either as halidohydrolases or oxygenases. Nevertheless, information is still severely lacking regarding the biochemical pathways involved in these processes, as well as their genetic control.A recently isolated Pseudomonas strain, named ES-2, was shown to possess a very wide degradative spectrum, and to contain at least one hydrolytic dehalogenase. The utilization by this organism of water-insoluble haloalkanes, such as 1-bromooctane, appears to consist of three phases: extracellular emulsification by a constitutively excreted surface active agent, periplasmic dehalogenation by an inducible dehalogenase, and intracellular degradation of the residual carbon skeleton.

SODIUM DEPRIVATION UNDER ALKALINE CONDITIONS CAUSES RAPID DEATH OF THE FILAMENTOUS CYANOBACTERIUM SPIRULINA PLATENSIS1

Like other alkaliphiles, the cyanobacterium Spirulina platensis (Norst.) Geitler requires sodium to function properly at elevated pH values. At pH 10.0, 150–250 mM Na+ were required for optimal growth, whereas 2.5 mM were sufficient for short‐term photosynthetic oxygen evolution. The complete absence of sodium, however, caused S. platensis to deteriorate. O2 evolution stopped, the absorbance at 620 nm corresponding to phycocyanin decreased, and the cells lysed within 1 h, a process accelerated by light. The activity of photosystem II, but not that of photosystem I, was affected in the process, which was irreversible unless sodium was readded within 15 minfrom the onset of the deprivation. The effect was mimicked, even in the presence of sodium, by the ionophore nigericin. We suggest that the cascade of events leading to cell lysis is primarily due to the inability of S. platensis to maintain a proton gradient (acid inside), possibly due to inactivity of a sodium/proton antiporter, as demonstrated for other alkaliphiles.

Effect of inorganic constituents on chemical oxygen demand—I. Bromides are unneutralizable by mercuric sulfate complexation

Abstract Chemical oxygen demand (COD) assays are widely used for the estimation of the organic carbon content of water and wastewater. The procedure is subject to interference by free halogen ions, the oxidation of which creates artificially high COD values. As part of an investigation of the interferences involved in the COD determination of chemical industries wastewaters, we found that mercuric sulfate complexation, the standard procedure for neutralizing the halogen effects, is suitable for chlorides but is not applicable to bromides. This observation is true both in the presence or absence of chloride or ammonia. Care should therefore be exercised in the interpretation of COD data for bromide-containing samples.

Effect of inorganic constituents on chemical oxygen demand—II. Organic carbon to halogen ratios determine halogen interference

Abstract The dependency of free halogen ion oxidation in chemical oxygen demand (COD) assays on the organic content of the sample was investigated. Halogen interference was reduced at increasing glucose or potassium hydrogen phthalate concentration; in each case, a threshold ratio of organic matter to halogen existed, above which halogen oxidation was masked. This ratio depended upon the presence of mercuric sulfate in the case of chloride but not of bromide. It was also affected by the ease of oxidation of both the organic molecule and the halogen ion, as well as by their actual COD. Thus, bromide oxidation was more difficult to prevent than that of chloride, and phthalate exerted a stronger masking effect than glucose.