Comparison of in vitro Antifungal Activity Methods Using Extract of Chitinase-producing Aeromonas sp. BHC02.

Biological control to prevent fungal plant diseases offers an alternative approach to facilitate sustainable agriculture. Since the chitin in fungal cell walls is a target for biocontrol agents, chitinases are one of the important antifungal molecules. In this study, the aim was to investigate a new chitinase isolated from a fluvial soil bacterium and to show the antifungal activity of the characterized chitinase by comparing the three common methods. The bacterium with the highest chitinase activity was identified as Aeromonas sp. by 16 S rRNA sequence analysis. Following the determination of the optimum enzyme production time, the enzyme was partially purified, and the physicochemical parameters of the enzyme were investigated. In the antifungal studies, direct Aeromonas sp. BHC02 cells or partially purified chitinase were used. As a result, in the first method in which the Aeromonas sp. BHC02 cells were spread on the surface of petri dishes, no zone formation was observed around the test fungi spotted on the surface. However, zone formation was observed in the methods in which the antifungal activity was investigated using the partially purified chitinase enzyme. For example, in the second method, the enzyme was spread on the surface of PDA, and zone formation was observed only around Penicillum species among the test fungi spotted on the surface. In the third method, in which the necessary time was given for the formation of mycelium of the test fungi, it was observed that the growth of Fusarium solani, Alternaria alternata and Botrytis cinerea was inhibited by the partially purified chitinase. This study concludes that the results of the antifungal activities depend on the method used and all fungal chitins cannot be degraded with one strain's chitinase. Depending on the variety of chitin, some fungi can be more resistant.

Effects of photodynamic therapy with indocyanine green on Streptococcus mutans biofilm.

BACKGROUND: The current procedures for treating tooth decay are not always guaranteed to successfully remove all microorganisms which cause disease. For elimination of bacteria and prevention of their effects, different methods are recommended, such as antibacterial materials and cavity disinfectants. The aim of this study was to compare the antibacterial activity of photodynamic therapy (PDT) using diode laser with indocyanin green (ICG) on Streptococcus (S.) mutans biofilm with conventional methods. METHODS: Ninety human molars were divided into 9 groups: negative control, positive control, CHX, NaOCl, gaseous ozone, erbium (Er):YAG laser, diode laser, and indocyanin green/ICG, and PDT. Cavities were then cut into the teeth (2 per tooth, 20 cavities per group) and sterilized. For all of the groups, with the exception of the negative control group, 105 CFU/mL of the active S. mutans culture were inoculated into the cavities and then incubated at 37 °C for 72 h. Then, dentin chips (25 ± 5 mg) were collected from cavity walls and spread on Mueller-Hinton agar media after decimal dilution. The colonies were counted after incubation at 37 °C for 24 h. RESULTS: All the treatments significantly reduced the number of S. mutans compared with the positive control group (p < 0.05). The antimicrobial effectiveness of CHX, NaOCl, ozone, PDT, Er:YAG laser, and diode laser groups were similar. The lowest bacterial reduction was observed in the ICGgroup. CONCLUSIONS: This work concludes that PDT using diode laser with ICG may be suggested on the cavity disinfection after caries excavation as an alternative to conventional methods.

Streptomyces sp. TEM 33 possesses high lipolytic activity in solid-state fermentation in comparison with submerged fermentation.

Solid-state fermentation (SSF) is a bioprocess that doesn't need an excess of free water, and it offers potential benefits for microbial cultivation for bioprocesses and product development. In comparing the antibiotic production, few detailed reports could be found with lipolytic enzyme production by Streptomycetes in SSF. Taking this knowledge into consideration, we prefer to purify Actinomycetes species as a new source for lipase production. The lipase-producing strain Streptomyces sp. TEM 33 was isolated from soil and lipase production was managed by solid-state fermentation (SSF) in comparison with submerged fermentation (SmF). Bioprocess-affecting factors like initial moisture content, incubation time, and various carbon and nitrogen additives and the other enzymes secreted into the media were optimized. Lipase activity was measured as 1.74 ± 0.0005 U/g dry substrate (gds) by the p-nitrophenylpalmitate (pNPP) method on day 6 of fermentation with 71.43% final substrate moisture content. In order to understand the metabolic priority in SSF, cellulase and xylanase activity of Streptomyces sp. TEM33 was also measured. The microorganism degrades the wheat bran to its usable form by excreting cellulases and xylanases; then it secretes the lipase that is necessary for degrading the oil in the medium.

Study of the TmoS/TmoT two-component system: towards the functional characterization of the family of TodS/TodT like systems.

The two-component system TmoS/TmoT controls the expression of the toluene-4-monooxygenase pathway in Pseudomonas mendocina RK1 via modulation of P(tmoX) activity. The TmoS/TmoT system belongs to the family of TodS/TodT like proteins. The sensor kinase TmoS is a 108 kDa protein composed of seven different domains. Using isothermal titration calorimetry we show that purified TmoS binds a wide range of aromatic compounds with high affinities. Tightest ligand binding was observed for toluene (K(D) = 150 nM), which corresponds to the highest affinity measured between an effector and a sensor kinase. Other compounds with affinities in the nanomolar range include benzene, the 3 xylene isomers, styrene, nitrobenzene or p-chlorotoluene. We demonstrate that only part of the ligands that bind to TmoS increase protein autophosphorylation in vitro and consequently pathway expression in vivo. These compounds are referred to as agonists. Other TmoS ligands, termed antagonists, failed to increase TmoS autophosphorylation, which resulted in their incapacity to stimulate gene expression in vivo. We also show that TmoS saturated with different agonists differs in their autokinase activities. The effector screening of gene expression showed that promoter activity of P(tmoX) and P(todX) (controlled by the TodS/TodT system) is mediated by the same set of 22 compounds. The common structural feature of these compounds is the presence of a single aromatic ring. Among these ligands, toluene was the most potent inducer of both promoter activities. Information on the TmoS/TmoT and TodS/TodT system combined with a sequence analysis of family members permits to identify distinct features that define this protein family.

Diversity at its best: bacterial taxis.

Bacterial taxis is one of the most investigated signal transduction mechanisms. Studies of taxis have primarily used Escherichia coli and Salmonella as model organism. However, more recent studies of other bacterial species revealed a significant diversity in the chemotaxis mechanisms which are reviewed here. Differences include the genomic abundance, size and topology of chemoreceptors, the mode of signal binding, the presence of additional cytoplasmic signal transduction proteins or the motor mechanism. This diversity of chemotactic mechanisms is partly due to the diverse nature of input signals. However, the physiological reasons for the majority of differences in the taxis systems are poorly understood and its elucidation represents a major research need.

Effects of biosorption parameter: kinetics, isotherm and thermodynamics for Ni(II) biosorption from aqueous solution by Circinella sp

Circinella sp. was employed as a biosorbent for removal of Ni(II) from aqueous solution. The biosorption kinetics and isotherms were investigated. The effect of several parameters, such as biosorbent dosage, contact time, initial concentration, pH and temperature, on biosorption process was evaluated. The kinetic studies indicated that the biosorption followed pseudo-second order kinetic model. Biosorption behaviour of Ni(II) on Circinella sp. was expressed by both Langmuir and Freundlich isotherms. The equilibrium data fit better to the Langmuir model compared to the Freundlich model in concentration range studied (1.0-3.0 mM). The thermodynamic parameters (AG°, AH° and AS°) were also determined, and it was found that the Ni(II) biosorption by Circinella sp. was spontaneous and endothermic in nature.