Regulatory elements in the 5'region of 16SrRNA gene of Bacillus sp. strain SJ-101

Isolation and characterization of a bisphenol A-degrading strain, Pseudomonas aeruginosa DU2, from soil containing decaying plants

Background and Objectives

Bisphenol A (BPA) is a toxic compound with broad applications in the plastics industry. BPA has harmful effects on various organisms and its efficient removal is necessary. The microbial degradation of BPA is a safe and economical approach. In this research, soil samples containing decaying plants were screened to isolate a BPA-degradable bacterial strain.

Materials and Methods

Soil samples were collected from different locations in Damghan, Semnan province, Iran. To enrich BPA-degrading bacteria, the samples were cultured in a stepwise manner in a mineral medium containing increasing BPA concentrations (5 to 40 mg/L). The ability of isolated bacteria in degrading BPA was assayed by Folin-Ciocalteu and high-performance liquid chromatography methods. The biodegradation efficiency of the most efficient isolate was assayed under distinct conditions and it was identified through the sequencing of the 16S rRNA gene.

Results

Among the isolated bacteria, Pseudomonas aeruginosa DU2 (GenBank accession number: OP919484) showed the most BPA biodegradation ability. The highest BPA degradation (52.98%) was observed in the mineral medium containing 5 mg/L BPA and the inoculum size of 6 × 107 CFU/mL at pH 9 and in the presence of 0.05% (w/v) NaCl during 10 days.

Conclusion

These results offer soil containing decaying plants as a promising source for finding BPA-degrading bacteria. P. aeruginosa DU2 has basal BPA removal ability, which could be improved by optimization of medium components and growth conditions.

Development and Application of Two Inducible Expression Systems for Streptococcus suis

Streptococcus suis is an important zoonotic bacterial pathogen posing a threat to the pig industry as well as public health, for which the mechanisms of growth and cell division remain largely unknown. Developing convenient genetic tools that can achieve strictly controlled gene expression is of great value for investigating these fundamental physiological processes of S. suis. In this study, we first identified three strong constitutive promoters, P_g, P_t, and P_e, in S. suis. Promoter P_g was used to drive the expression of repressor genes tetR and lacI, and the operator sequences were added within promoters P_t and P_e. By optimizing the insertion sites of the operator sequence, we successfully constructed an anhydrotetracycline (ATc)-inducible expression system and an isopropyl-β-d-thiogalactopyranoside (IPTG)-inducible expression system in S. suis. We showed that these two systems provided inducer-concentration- and induction-time-dependent expression of the reporter gene. By using these tools, we investigated the subcellular localization of a key cell division protein, FtsZ, which showed that it could be correctly localized to the midcell region. In addition, we constructed a conditional knockout strain for the glmS gene, which is an essential gene, and showed that our ATc-inducible promoter could provide strictly controlled expression of glmS in trans, suggesting that our inducible expression systems can be used for deletion of essential genes in S. suis. Therefore, for the first time we developed two inducible expression systems in S. suis and showed their applications in the study of an important cell division protein and an essential gene. These genetic tools will further facilitate the functional study of other important genes of S. suis. IMPORTANCE Streptococcus suis is an important zoonotic bacterial pathogen. Studying the mechanisms of cell growth and division is important for the identification of novel antimicrobial drug targets. Inducible expression systems can provide strictly controlled expression of the protein of interest and are useful tools to study the functions of physiologically important proteins. However, there is a lack of convenient genetic tools that can achieve inducible protein expression in S. suis. In this study, we developed two (ATc-inducible and IPTG-inducible) inducible expression systems and showed their applications in a subcellular localization study of a cell division protein and the construction of conditional knockout of essential genes in S. suis. These systems will be useful for functional studies of important proteins of S. suis.

Macrocystis pyrifera source of nutrients for the production of carotenoids by a marine yeast Rhodotorula mucilaginosa

AIMS

To evaluate an aqueous extract of Macrocystis pyrifera as a nutrient source for the production of carotenoids by a marine Rhodotorula mucilaginosa isolated from seaweed samples.

MATERIALS AND RESULTS

The effect of different culture conditions on the concentration of biomass and total pigments was evaluated using a Box-Behnken experimental design. The seaweed extract contained 15% w w-1 of protein and 20% w w-1 of carbohydrate; the main sugar in this fraction was trehalose (78%). The culture conditions that maximize the total pigment concentration (1·84 ± 0·03 mg l-1 ) were initial pH equal to 7, yeast extract as nitrogen source at a concentration of 4 g l-1 , seaweed extract concentration at 25% v v-1 , incubation performed at 25°C and 150 rev min-1 during 6 days. Under optimal growth conditions, three carotenoids were identified among the pigments produced by R. mucilaginosa, lycopene (38·4 ± 9·4%), β-carotene (21·8 ± 1·5%) and astaxanthin (1·8 ± 0·3%).

CONCLUSIONS

Carotenoids of commercial interest (lycopene, β-carotene and astaxanthin) can be produced using a marine R. mucilaginosa cultivated with an aqueous extract of M. pyrifera as nutrient source. The total pigment concentration in the culture ranged between 0·82 and 1·84 mg l-1 , and was significantly affected by the concentration of the seaweed extract, and yeast extract.

SIGNIFICANCE AND IMPACT OF THE STUDY

This work demonstrates that M. pyrifera can be used as a nutrient source for the production of carotenoids by the marine yeast.

Adsorption of Cu2+ and mechanism by natural biofilm

The biofilm culturing device fixed on the slides was vertically placed in the commonly called small Li Lake of Jiangnan University. The adsorption experiment of Cu²⁺ was carried out by mature biofilm. Besides, scanning electron microscope (SEM), polymerase chain reaction and denaturing gradient gel electrophoresis (PCR-DGGE), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy-energy spectrum (SEM-EDX) were used to analysis the effect of Cu²⁺ on the morphological structure of biofilm. The result indicated that when the initial concentration of Cu²⁺ was 5 mg·L^-1, the absorption capacity of Cu²⁺ by unit mass biofilm is the maximum. More extracellular polymeric substances (EPS) were released by biofilm due to the stimulation of Cu²⁺. EPS was beneficial to the adsorption of Cu²⁺ by biofilm. After the adsorption of Cu²⁺, the bacterial diversity index decreased, while there were no significant differences in microbial communities on biofilm. Moreover, the main groups combining Cu²⁺ were the hydroxyl groups and amide groups in S-EPS and B-EPS. Ion exchange is a mechanism of the adsorption of Cu²⁺ by EPS.

Enhanced production of l-sorbose in an industrial Gluconobacter oxydans strain by identification of a strong promoter based on proteomics analysis

Gluconobacter oxydans is capable of rapidly incomplete oxidation of many sugars and alcohols, which means the strain has great potential for industrial purposes. Strong promoters are one of the essential factors that can improve strain performance by overexpression of specific genes. In this study, a pipeline for screening strong promoters by proteomics analysis was established. Based on the procedure, a new strong promoter designated as PB932_2000 was identified in G. oxydans WSH-003. The promoter region was characterized based on known genome sequence information using BPROM. The strength of PB932_2000 was further assessed by analysis of enhanced green fluorescent protein (egfp) expression and comparison with egfp expression by two commonly used strong promoters, PE. coli_tufB and PG. oxydans_tufB. Both quantitative real-time PCR and fluorescence intensities for egfp gene expression showed that PB932_2000 promoter is stronger than the other two. Overexpression of d-sorbitol dehydrogenase (sldh) by PB932_2000 in G. oxydans WSH-003 enhanced the titer and productivity of l-sorbose synthesis from d-sorbitol by 12.0 % and 33.3 %, respectively. These results showed that proteomics analysis is an efficient way to identify strong promoters. The isolated promoter PB932_2000 could further facilitate the metabolic engineering of G. oxydans.

Isolation, identification and computational studies on Pseudomonas aeruginosa sp. strain MPC1 in tannery effluent

A study about isolation, identification and analysis of bacteria in waste water. Here the tannery effluent used as a sample for the entire analysis. A bacterial strain, designated MPC1 was isolated from a waste water sample collected from tannery effluent, Trichy, India and identified using a molecular approach. On the basis of the bacterial 16s rRNA gene sequence phylogeny and comparison of this gene sequence with sequence in RNA sequence database, it is considered that isolate is closely related to members of the Pseudomonas aeruginosa Sp. Phylogenetic and molecular evolutionary analyses were conducted using MEGA. Identification of regulatory elements and Transcription Factor with their binding sites in 16S rRNA gene of Pseudomonas aeruginosa mpc1 was performed using BPROM tool. The sequence of 16s rRNA (Pseudomonas aeruginosa sp MPC 1) is submitted to Genbank in NCBI database (Ac.No-JF708077).