Forgot your password?
New user?
New Window Opens on the Secret Life of Microbes: Scientists Develop First Microbial Profiles of Ecosystems
CAS announces the release of SciFinder Scholar for Mac OS X
Press Releases
Press Releases
| Check out our New Publishers' Select for Free Articles |
Archives of Microbiology (v.193, #8)
Evaluation of pink-pigmented facultative methylotrophic bacteria for phosphate solubilization by Shanmugam Jayashree; Ponnusamy Vadivukkarasi; Kirupanithi Anand; Yuko Kato; Sundaram Seshadri (pp. 543-552).
Thirteen pink-pigmented facultative methylotrophic (PPFM) strains isolated from Adyar and Cooum rivers in Chennai and forest soil samples in Tamil Nadu, India, along with Methylobacterium extorquens, M. organophilum, M. gregans, and M. komagatae were screened for phosphate solubilization in plates. P-solubilization index of the PPFMs grown on NBRIP—BPB plates for 7 days ranged from 1.1 to 2.7. The growth of PPFMs in tricalcium phosphate amended media was found directly proportional to the glucose concentration. Higher phosphate solubilization was observed in four strains MSF 32 (415 mg l−l), MDW 80 (301 mg l−l), M. komagatae (279 mg l−l), and MSF 34 (202 mg l−l), after 7 days of incubation. A drop in the media pH from 6.6 to 3.4 was associated with an increase in titratable acidity. Acid phosphatase activity was more pronounced in the culture filtrate than alkaline phosphatase activity. Adherence of phosphate to densely grown bacterial surface was observed under scanning electron microscope after 7-day-old cultures. Biochemical characterization and screening for methanol dehydrogenase gene (mxaF) confirmed the strains as methylotrophs. The mxaF gene sequence from MSF 32 clustered towards M. lusitanum sp. with 99% similarity. This study forms the first detailed report on phosphate solubilization by the PPFMs.
Keywords: Acid phosphatase; Alkaline phosphatase; River water; Forest soil; mxaF
Purification and characterization of benzyl alcohol- and benzaldehyde- dehydrogenase from Pseudomonas putida CSV86 by Rahul Shrivastava; Aditya Basu; Prashant S. Phale (pp. 553-563).
Pseudomonas putida CSV86 utilizes benzyl alcohol via catechol and methylnaphthalenes through detoxification pathway via hydroxymethylnaphthalenes and naphthaldehydes. Based on metabolic studies, benzyl alcohol dehydrogenase (BADH) and benzaldehyde dehydrogenase (BZDH) were hypothesized to be involved in the detoxification pathway. BADH and BZDH were purified to apparent homogeneity and were (1) homodimers with subunit molecular mass of 38 and 57 kDa, respectively, (2) NAD+ dependent, (3) broad substrate specific accepting mono- and di-aromatic alcohols and aldehydes but not aliphatic compounds, and (4) BADH contained iron and magnesium, while BZDH contained magnesium. BADH in the forward reaction converted alcohol to aldehyde and required NAD+, while in the reverse reaction it reduced aldehyde to alcohol in NADH-dependent manner. BZDH showed low K m value for benzaldehyde as compared to BADH reverse reaction. Chemical cross-linking studies revealed that BADH and BZDH do not form multi-enzyme complex. Thus, the conversion of aromatic alcohol to acid is due to low K m and high catalytic efficiency of BZDH. Phylogenetic analysis revealed that BADH is a novel enzyme and diverged during the evolution to gain the ability to utilize mono- and di-aromatic compounds. The wide substrate specificity of these enzymes enables strain to detoxify methylnaphthalenes to naphthoic acids efficiently.
Keywords: Benzyl alcohol dehydrogenase; Benzaldehyde dehydrogenase; Purification and kinetic constants; Protein–protein interactions; Substrate specificity; Phylogenetic analysis
Functions of a hemolysin-like protein in the cyanobacterium Synechocystis sp. PCC 6803 by Tetsushi Sakiyama; Hiroya Araie; Iwane Suzuki; Yoshihiro Shiraiwa (pp. 565-571).
A glucose-tolerant strain of the cyanobacterium Synechocystis sp. PCC 6803, generally referred to as wild type, produces a hemolysin-like protein (HLP) located on the cell surface. To analyze the function of HLP, we constructed a mutant in which the hlp gene was disrupted. The growth rate of the mutant was reduced when the cells were stressed by treatment with CuSO4, CdCl2, ZnCl2, ampicillin, kanamycin, or sorbitol in liquid medium, suggesting that HLP may increase cellular resistance to the inhibitory effects of these compounds. Uptake assays with 109Cd2+ using the silicone–oil layer centrifugation technique revealed that both wild type and mutant cells were labeled with 109Cd2+ within 1 min. Although the total radioactivity was much higher in the wild-type cells, 109Cd2+ incorporation was clearly much higher in the mutant cells after adsorbed 109Cd2+ was removed from the cell surface by washing with EDTA. These findings suggest that HLP functions as a barrier against the adsorption of toxic compounds.
Keywords: Cell wall; Heavy metal stress; Hemolysin-like protein; S-layer; Cyanobacterium
Chromocurvus halotolerans gen. nov., sp. nov., a gammaproteobacterial obligately aerobic anoxygenic phototroph, isolated from a Canadian hypersaline spring by J. T. Csotonyi; E. Stackebrandt; J. Swiderski; P. Schumann; V. Yurkov (pp. 573-582).
A strain EG19T of aerobic bacteria able to form pleomorphic cells was isolated from a brine spring runoff stream in the west central region of the province of Manitoba, Canada. The pale pinkish purple strain contained bacteriochlorophyll a incorporated into light-harvesting I and reaction center complexes. Its inability to grow under anaerobic illuminated conditions prompted designation as a member of the functional group known as aerobic anoxygenic phototrophic bacteria. Phylogenetic analysis of the 16S rRNA gene sequence revealed that it belonged to the Gammaproteobacteria, forming a distinct branch of phototrophs distantly related to most described aerobic anoxygenic phototrophs, quite marginally related (95.6%) both to the only other described gammaproteobacterial aerobic phototroph, Congregibacter litoralis, and also to nonphototrophs in the genus Haliea (95.1–96.1%). Physiological tests demonstrated tolerance profiles to salinity (0–18% NaCl), pH (7–12), and temperature (7–40°C) consistent with survival in a shallow hypersaline stream on the exposed, vegetation-depleted salt playa of its native East German Creek. Phylogenetic data and phenotypic properties such as pigment composition, morphology, and physiology support the proposal of the novel genus and species Chromocurvus halotolerans gen. nov., sp. nov., with EG19T (=DSM 23344T, =VKM B-2659T) as the type strain.
Keywords: Chromocurvus halotolerans ; Aerobic anoxygenic phototrophs; Bacteriochlorophyll a ; Gammaproteobacteria
Expression of the bifunctional Bacillus subtilis TatAd protein in Escherichia coli reveals distinct TatA/B-family and TatB-specific domains by James P. Barnett; Janna Lawrence; Sharon Mendel; Colin Robinson (pp. 583-594).
In the Tat protein export pathway of Gram-negative bacteria, TatA and TatB are homologous proteins that carry out distinct and essential functions in separate sub-complexes. In contrast, Gram-positive Tat systems usually lack TatB and the TatA protein is bifunctional. We have used a mutagenesis approach to delineate TatA/B-type domains in the bifunctional TatAd protein from Bacillus subtilis. This involved expression of mutated TatAd variants in Escherichia coli and tests to determine whether the variants could function as TatA or TatB by complementing E. coli tatA and/or tatB mutants. We show that mutations in the C-terminal half of the transmembrane span and the subsequent FGP ‘hinge’ motif are critical for TatAd function with its partner TatCd subunit, and the same determinants are required for complementation of either tatA or tatB mutants in Escherichia coli. This is thus a critical domain in both TatA and TatB proteins. In contrast, substitution of a series of residues at the N-terminus specifically blocks the ability of TatAd to substitute for E. coli TatB. The results point to the presence of a universally conserved domain in the TatA/B-family, together with a separate N-terminal domain that is linked to the TatB-type function in Gram-negative bacteria.
Keywords: Tat; Twin-arginine; Protein transport; Signal peptide
Genetic variability of the invasive cyanobacteria Cylindrospermopsis raciborskii from Bir M’cherga reservoir (Tunisia) by Afef Fathalli; Amel Ben Rejeb Jenhani; Cristiana Moreira; Joana Azevedo; Martin Welker; Mohamed Romdhane; Agostinho Antunes; Vitor Vasconcelos (pp. 595-604).
Cylindrospermopsis raciborskii is an invasive freshwater cyanobacteria of tropical origin, also found in temperate regions. Due to its known ability to produce potent toxins, such as cylindrospermopsin and the paralytic shellfish poisoning, this species is of major concern from a water quality perspective. This study presents a genetic characterization of four C. raciborskii strains isolated from the Bir M’cherga Tunisian reservoir. The toxicity assessment was investigated via molecular biology tools, which suggested that all the isolated strains were not producing cylindrospermopsin, saxitoxin, or microcystin. This result was further confirmed by HPLC and MALDI-TOF analyses. However, we report for the first time in C. raciborskii the presence of mcyA and mcyE, two segments of the microcystin synthetase mcy cluster. All the strains were identified taxonomically based on the 16S rRNA sequences, and their phylogenetic relationships were assessed using the rpoC1 region. Tunisian strains formed a distinct clade separated from the other African strains.
Keywords: Cylindrospermopsis raciborskii ; Toxicity; mcyA and mcyE ; Phylogenetic analysis; Tunisia
Mn(II) oxidation in Pseudomonas putida GB-1 is influenced by flagella synthesis and surface substrate by Kati Geszvain; Ai Yamaguchi; Jared Maybee; Bradley M. Tebo (pp. 605-614).
Bacterially mediated manganese(II) oxidation greatly affects the biogeochemical cycling of Mn and other elements. One species of bacteria that are capable of Mn(II) oxidation is the gamma-proteobacterium Pseudomonas putida GB-1. In this organism, Mn(II) oxidation begins in stationary phase on the outer surface of the cell, forming a layer of insoluble Mn(III,IV) oxides. A random transposon mutagenesis screen isolated 12 mutant strains of P. putida GB-1 that exhibited increased Mn(II) oxidation on solid media relative to wild type. In 8 out of the 12 strains, the transposon had inserted into a putative flagellar gene. Those 8 strains each had motility defects, thus the disrupted genes are part of the P. putida GB-1 flagellar regulon. The flagellar genes identified include putative structural components (FliC, FliD, FlgE, and FlgL) and regulatory proteins (FlgM and FleN). Deletion of either the FleN gene (fleN) or the overlapping gene fliA resulted in increased Mn(II) oxidation, while in-frame deletion of fliF, which encodes an essential component of the basal body, did not. In liquid media, the flagellar mutants exhibited delayed Mn(II) oxidation relative to wild type. These results suggest that bacterial Mn(II) oxidation is regulated in part by flagellar-mediated responses to the surface substrate.
Keywords: Mn(II) oxidation; Flagella; Motility; Pseudomonas putida GB-1; Biofilm