Factors influencing the activity of cellular alkaline phosphatase during growth and sporulation of Bacillus cereus

Roles of Phosphorus Sources in Microbial Community Assembly for the Removal of Organic Matters and Ammonia in Activated Sludge

Various phosphorus sources are utilized by microbes in WWTPs, eventually affecting microbial assembly and functions. This study identified the effects of phosphorus source on microbial communities and functions in the activated sludge. By cultivation with 59 phosphorus sources, including inorganic phosphates (IP), nucleoside-monophosphates (NMP), cyclic-nucleoside-monophosphates (cNMP), and other organophosphates (OP), we evaluated the change in removal efficiencies of total organic carbon (TOC) and ammonia, microbial biomass, alkaline phosphatase (AKP) activity, microbial community structure, and AKP-associated genes. TOC and ammonia removal efficiency was highest in IP (64.8%) and cNMP (52.3%) treatments. Microbial community structure changed significantly across phosphorus sources that IP and cNMP encouraged Enterobacter and Aeromonas, respectively. The abundance of phoA and phoU genes was higher in IP treatments, whereas phoD and phoX genes dominated OP treatments. Our findings suggested that the performance of WWTPs was dependent on phosphorus sources and provided new insights into effective WWTP management.

Monitoring the effect of chemicals on biological communities. The biofilm as an interface

Biofilms can be regarded as early warning systems for detection of the effects of toxicants on aquatic systems, because they have been successfully used for detection of other environmental stressors (e.g. pH, salinity, organic pollution). A variety of methods is used for detection of the effects of toxicants by use of biofilms. The methods range from structurally-based to functionally-based, and from in vitro-based to systemic approaches. Physiological approaches may be appropriate for detection of acute effects. Among these methods, photosynthesis is more related to the effect of toxicants affecting algal communities, directly or indirectly, and extracellular enzyme activity is less specific. Selecting one or the other may depend on the suspected direct effect of the toxicant. Integrated studies have revealed the relevance of toxicants to top-down or bottom-up regulation of the biofilm community. Persistent or chronic effects should affect other biofilm indicators, for example growth or biomass-related factors (e.g. chlorophyll), or community composition. Among these, community composition might better reflect the effects of the toxicant(s), because this may cause a shift from a sensitive to a progressively tolerant community. Community composition-based approaches do not usually adequately reflect cause-effect relationships and require complementary analysis of properties affected in the short-term, for example physiological properties. The current array of methods available must be wisely combined to disentangle the effects of chemicals on biofilms, and whether these effects are transient or persistent, to successfully translate the chemical action of toxicants into the effect they might have on the river ecosystem.

A phosphate-stimulated NAD(P)+-dependent glyceraldehyde-3-phosphate dehydrogenase in Bacillus cereus

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH), a key enzyme of central carbon metabolism, was studied in a Bacillus cereus strain isolated from the phosphate layer from Morocco. Enzymatic assays with cell extracts demonstrated that when grown on Luria-Bertani (LB) medium, B. cereus contains a major NAD+-dependent GAPDH activity and only traces of NADP+-dependent activity, but in cells grown on Pi-supplemented LB medium a strong increase of the NADP+-dependent activity, that became predominant, occurs concurrently with a GAPDH protein increase. Our results show that B. cereus possesses two GAPDH activities, namely NAD+- and NADP+-dependent, catalyzed by two enzymes with distinct coenzyme specificity and different phosphate regulation patterns. The finding of a phosphate-stimulated NADP+-dependent GAPDH in B. cereus indicates that this bacterium can modulate its primary carbon metabolism according to phosphate availability.

Alkaline phosphatase production during sporulation of Bacillus cereus

Cell-bound alkaline phosphatase of Bacillus cereus was produced during vegetative growth and sporulation in a complex medium. Addition of glucose repressed the sporulation process and the amount of enzyme synthesized increased. The time course of alkaline phosphatase production is very similar in both sporulating and non-sporulating cells. Irrespective of sporulation, alkaline phosphatase level shows a peak of activity in the exponential phase, and another in the stationary phase of growth. This preliminary data indicates differences between B. cereus, and B. subtilis in alkaline phosphatase characteristics.