Journal of Microbiology

Volume 54(2); February 2016

Review

MINIREVIEW] Biofilm dispersion in Pseudomonas aeruginosa: Soo-Kyoung Kim , Joon-Hee Lee; J. Microbiol. 2016;54(2):71-85. Published online February 2, 2016; DOI: https://doi.org/10.1007/s12275-016-5528-7

14 View
0 Download
100 Citations

Abstract: In recent decades, many researchers have written numerous articles about microbial biofilms. Biofilm is a complex community of microorganisms and an example of bacterial group behavior. Biofilm is usually considered a sessile mode of life derived from the attached growth of microbes to surfaces, and most biofilms are embedded in self-produced extracellular matrix composed of extracellular polymeric substances (EPSs), such as polysaccharides, extracellular DNAs (eDNA), and proteins. Dispersal, a mode of biofilm detachment indicates active mechanisms that cause individual cells to separate from the biofilm and return to planktonic life. Since biofilm cells are cemented and surrounded by EPSs, dispersal is not simple to do and many researchers are now paying more attention to this active detachment process. Unlike other modes of biofilm detachment such as erosion or sloughing, which are generally considered passive processes, dispersal occurs as a result of complex spatial differentiation and molecular events in biofilm cells in response to various environmental cues, and there are many biological reasons that force bacterial cells to disperse from the biofilms. In this review, we mainly focus on the spatial differentiation of biofilm that is a prerequisite for dispersal, as well as environmental cues and molecular events related to the biofilm dispersal. More specifically, we discuss the dispersal-related phenomena and mechanisms observed in Pseudomonas aeruginosa, an important opportunistic human pathogen and representative model organism for biofilm study.

Journal Article

Molecular diversity and distribution of indigenous arbuscular mycorrhizal communities colonizing roots of two different winter cover crops in response to their root proliferation: Masao Higo , Katsunori Isobe , Yusuke Miyazawa , Yukiya Matsuda , Rhae A. Drijber , Yoichi Torigoe; J. Microbiol. 2016;54(2):86-97. Published online February 2, 2016; DOI: https://doi.org/10.1007/s12275-016-5379-2

10 View
0 Download
20 Citations

Abstract: A clear understanding of how crop root proliferation affects the distribution of the spore abundance of arbuscular mycorrhizal fungi (AMF) and the composition of AMF communities in agricultural fields is imperative to identify the potential roles of AMF in winter cover crop rotational systems. Toward this goal, we conducted a field trial using wheat (Triticum aestivum L.) or red clover (Trifolium pratense L.) grown during the winter season. We conducted a molecular analysis to compare the diversity and distribution of AMF communities in roots and spore abundance in soil cropped with wheat and red clover. The AMF spore abundance, AMF root colonization, and abundance of root length were investigated at three different distances from winter crops (0 cm, 7.5 cm, and 15 cm), and differences in these variables were found between the two crops. The distribution of specific AMF communities and variables responded to the two winter cover crops. The majority of Glomerales phylotypes were common to the roots of both winter cover crops, but Gigaspora phylotypes in Gigasporales were found only in red clover roots. These
results
also demonstrated that the diversity of the AMF colonizing the roots did not significantly change with the three distances from the crop within each rotation but was strongly influenced by the host crop identity. The distribution of specific AMF phylotypes responded to the presence of wheat and red clover roots, indicating that the host crop identity was much more important than the proliferation of crop roots in determining the diversity of the AMF communities.

Research Support, Non-U.S. Gov't

The effect of the cwf14 gene of fission yeast on cell wall integrity is associated with rho1: Dong-Uk Kim , Shinae Maeng , Hyemi Lee , Miyoung Nam , Sook-Jeong Lee , Kwang-Lae Hoe; J. Microbiol. 2016;54(2):98-105. Published online February 2, 2016; DOI: https://doi.org/10.1007/s12275-016-5569-y

13 View
0 Download
2 Citations

Abstract: In all eukaryotic organisms, a wide range of morphologies are responsible for critical cellular function and development. In particular, the Rho GTPases, which are highly conserved from yeast to mammals, are key molecules in signaling pathways that control cell polarity processes and cell wall biosynthesis, which are fundamental aspects of morphogenesis. Therefore, using haploinsufficiency deletion mutants of the fission yeast Schizosaccharomyces pombe, we screened the slow-growing mutants and their morphogenesis, specifically focusing on regulation of their Rho GTPases. Based on this screening, we found that the cwf14 mutant of S. pombe exhibited the slow growth and abnormal phenotypes with an elongated cell shape and thicker cell wall when compared with wild-type cells. In particular, cells with the cwf14 deletion showed excessive Rho1 expression. However, the wildtype strain with ectopically expressed Rho1 did not exhibited any significant change in the level of cwf14, suggesting that cwf14 may act on the upstream of Rho1. Furthermore, the cells with a cwf14 deletion also have increased sensitivity to β-glucanase, a cell wall-digesting enzyme, which is also seen in Rho1-overexpressing cells. Overall, our results suggest that the cwf14 plays a key role in fission yeast morphogenesis and cell wall biosynthesis and/or degradation possibly via the regulation of Rho1 expression.

Journal Article

Kinetic characterization of a novel acid ectophosphatase from Enterobacter asburiae: Vanessa Sayuri Sato , Renato F. Galdiano Júnior , Gisele Regina Rodrigues , Eliana G. M. Lemos , João Martins Pizauro Junior; J. Microbiol. 2016;54(2):106-113. Published online February 2, 2016; DOI: https://doi.org/10.1007/s12275-015-5354-3

10 View
0 Download
7 Citations

Abstract: Expression of acid ectophosphatase by Enterobacter asburiae, isolated from Cattleya walkeriana (Orchidaceae) roots and identified by the 16S rRNA gene sequencing analysis, was strictly regulated by phosphorus ions, with its optimal activity being observed at an inorganic phosphate concentration of 7 mM. At the optimum pH 3.5, intact cells released p-nitrophenol at a rate of 350.76 ± 13.53 nmol of p-nitrophenolate (pNP)/min/108 cells. The membrane-bound enzyme was obtained by centrifugation at 100,000 × g for 1 h at 4°C. p-Nitrophenylphosphate (pNPP) hydrolysis by the enzyme follows “Michaelis-Menten” kinetics with V = 61.2 U/mg and K0.5 = 60 μM, while ATP hydrolysis showed V = 19.7 U/mg, K0.5 = 110 μM, and nH = 1.6 and pyrophosphate hydrolysis showed V = 29.7 U/mg, K0.5 = 84 μM, and nH = 2.3. Arsenate and phosphate were competitive inhibitors with Ki = 0.6 mM and Ki = 1.8 mM, respectively. p-Nitrophenyl phosphatase (pNPPase) activity was inhibited by vanadate, while p-hydroxymercuribenzoate, EDTA, calcium, copper, and cobalt had no inhibitory effects. Magnesium ions were stimulatory (K0.5 = 2.2 mM and nH = 0.5). Production of an acid ectophosphatase can be a mechanism for the solubilization of mineral phosphates by microorganisms such as Enterobacter asburiae that are versatile in the solubilization of insoluble minerals, which, in turn, increases the availability of nutrients for plants, particularly in soils that are poor in phosphorus.

Research Support, Non-U.S. Gov'ts

Crystal structure and modeling of the tetrahedral intermediate state of methylmalonate-semialdehyde dehydrogenase (MMSDH) from Oceanimonas doudoroffii: Hackwon Do , Chang Woo Lee , Sung Gu Lee , Hara Kang , Chul Min Park , Hak Jun Kim , Hyun Park , HaJeung Park , Jun Hyuck Lee; J. Microbiol. 2016;54(2):114-121. Published online February 2, 2016; DOI: https://doi.org/10.1007/s12275-016-5549-2

10 View
0 Download
6 Citations

Abstract: The gene product of dddC (Uniprot code G5CZI2), from the Gram-negative marine bacterium Oceanimonas doudoroffii, is a methylmalonate-semialdehyde dehydrogenase (OdoMMSDH) enzyme. MMSDH is a member of the aldehyde dehydrogenase superfamily, and it catalyzes the NADdependent decarboxylation of methylmalonate semialdehyde to propionyl-CoA. We determined the crystal structure of OdoMMSDH at 2.9 Å resolution. Among the twelve molecules in the asymmetric unit, six subunits complexed with NAD, which was carried along the protein purification steps. OdoMMSDH exists as a stable homodimer in solution; each subunit consists of three distinct domains: an NAD-binding domain, a catalytic domain, and an oligomerization domain. Computational modeling studies of the OdoMMSDH structure revealed key residues important for substrate recognition and tetrahedral intermediate stabilization. Two basic residues (Arg103 and Arg279) and six hydrophobic residues (Phe150, Met153, Val154, Trp157, Met281, and Phe449) were found to be important for tetrahedral intermediate binding. Modeling data also suggested that the backbone amide of Cys280 and the side chain amine of Asn149 function as the oxyanion hole during the enzymatic reaction. Our results provide useful insights into the substrate recognition site residues and catalytic mechanism of OdoMMSDH.

TatC-dependent translocation of pyoverdine is responsible for the microbial growth suppression: Yeji Lee , Yong-Jae Kim , Jung-Hoon Lee , Hyung Eun Yu , Kiho Lee , Shouguang Jin , Un-Hwan Ha; J. Microbiol. 2016;54(2):122-130. Published online February 2, 2016; DOI: https://doi.org/10.1007/s12275-016-5542-9

9 View
0 Download
4 Citations

Abstract: Infections are often not caused by a colonization of Pseudomonas aeruginosa alone but by a consortium of other bacteria. Little is known about the impact of P. aeruginosa on the growth of other bacteria upon coinfection. Here, cellree culture supernatants obtained from P. aeruginosa suppressed the growth of a number of bacterial strains such as Corynebacterium glutamicum, Bacillus subtilis, Staphylococcus aureus, and Agrobacterium tumefaciens, but had little effect on the growth of Escherichia coli and Salmonella Typhimurium. The growth suppression effect was obvious when P. aeruginosa was cultivated in M9 minimal media, and the suppression was not due to pyocyanin, a well-known antimicrobial toxin secreted by P. aeruginosa. By performing transposon mutagenesis, PA5070 encoding TatC was identified, and the culture supernatant of its mutant did not suppress the growth. HPLC analysis of supernatants showed that pyoverdine was a secondary metabolite present in culture supernatants of the wild-type strain, but not in those of the PA5070 mutant. Supplementation of FeCl2 as a source of iron compromised the growth suppression effect of supernatants and also recovered biofilm formation of S. aureus, indicating that pyoverdine-mediated iron acquisition is responsible for the growth suppression. Thus, this study provides the action of TatC-dependent pyoverdine translocation for the growth suppression of other bacteria, and it might aid understanding of the impact of P. aeruginosa in the complex community of bacterial species upon coinfection.

Antibacterial metabolites from the Actinomycete Streptomyces sp. P294: Huining Su , Hongwei Shao , Keqin Zhang , Guohong Li; J. Microbiol. 2016;54(2):131-135. Published online February 2, 2016; DOI: https://doi.org/10.1007/s12275-016-5311-9

10 View
0 Download
8 Citations

Abstract: The Actinomycete strain P294 was isolated from soil and identified as Streptomyces sp. based upon the results of 16S rRNA sequence analysis. Three compounds obtained from the solid fermentation products of this strain have been determined by 1D, 2D NMR and HRMS experiments. These compounds include two new compounds angumycinones C (1) and D (2), and the known compound X-14881 E (3). All compounds were assayed for antibacterial and nematicidal activity. The results showed the three compounds had different degrees of inhibitory activity against several target bacteria but no significant toxicity against the nematode Caenorhabditis elegans.

Inhibition of eukaryotic translation by tetratricopeptide-repeat proteins of Orientia tsutsugamushi: Sunyoung Bang , Chan-Ki Min , Na-Young Ha , Myung-Sik Choi , Ik-Sang Kim , Yeon-Sook Kim , Nam-Hyuk Cho; J. Microbiol. 2016;54(2):136-144. Published online February 2, 2016; DOI: https://doi.org/10.1007/s12275-016-5599-5

10 View
0 Download
8 Citations

Abstract: Orientia tsutsugamushi, an obligate intracellular bacterium, is the causative agent of scrub typhus. The genome of Orientia tsutsugamushi has revealed multiple ORFs encoding tetratricopeptide- repeat (TPR) proteins. The TPR protein family has been shown to be involved in a diverse spectrum of cellular functions such as cell cycle control, transcription, protein transport, and protein folding, especially in eukaryotic cells. However, little is known about the function of the TPR proteins in O. tsutsugamushi. To investigate the potential role of TPR proteins in host-pathogen interaction, two oriential TPR proteins were expressed in E. coli and applied for GSTpull down assay. DDX3, a DEAD-box containing RNA helicase, was identified as a specific eukaryotic target of the TPR proteins. Since the RNA helicase is involved in multiple RNAmodifying processes such as initiation of translation reaction, we performed in vitro translation assay in the presence of GST-TPR fusion proteins by using rabbit reticulocyte lysate system. The TPR proteins inhibited in vitro translation of a reporter luciferase in a dose dependent manner whereas the GST control proteins did not. These results suggested TPR proteins of O. tsutsugamushi might be involved in the modulation of eukarytotic translation through the interaction with DDX3 RNA helicase after secretion into host cytoplasm.

First
Prev
Page of 1
Next
Last

Previous issues