Journal of Microbiology

Volume 52(9); September 2014

Review

Minireveiw] Urban Microbiomes and Urban Ecology: How Do Microbes in the Built Environment Affect Human Sustainability in Cities?: Gary M. King; J. Microbiol. 2014;52(9):721-728. Published online September 2, 2014; DOI: https://doi.org/10.1007/s12275-014-4364-x

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46 Citations

Abstract: Humans increasingly occupy cities. Globally, about 50% of the total human population lives in urban environments, and in spite of some trends for deurbanization, the transition from rural to urban life is expected to accelerate in the future, especially in developing nations and regions. The Republic of Korea, for example, has witnessed a dramatic rise in its urban population, which now accounts for nearly 90% of all residents; the increase from about 29% in 1955 has been attributed to multiple factors, but has clearly been driven by extraordinary growth in the gross domestic product accompanying industrialization. While industrialization and urbanization have unarguably led to major improvements in quality of life indices in Korea and elsewhere, numerous serious problems have also been acknowledged, including concerns about resource availability, water quality, amplification of global warming and new threats to health. Questions about sustainability have therefore led Koreans and others to consider deurbanization as a management policy. Whether this offers any realistic prospects for a sustainable future remains to be seen. In the interim, it has become increasingly clear that built environments are no less complex than natural environments, and that they depend on a variety of internal and external connections involving microbes and the processes for which microbes are responsible. I provide here a definition of the urban microbiome, and through examples indicate its centrality to human function and wellbeing in urban systems. I also identify important knowledge gaps and unanswered questions about urban microbiomes that must be addressed to develop a robust, predictive and general understanding of urban biology and ecology that can be used to inform policy-making for sustainable systems.

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

Luteimonas dalianensis sp. nov., an Obligate Marine Bacterium Isolated from Seawater: Yanjuan Xin , Xupeng Cao , Peichun Wu , Song Xue; J. Microbiol. 2014;52(9):729-733. Published online August 2, 2014; DOI: https://doi.org/10.1007/s12275-014-3610-6

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16 Citations

Abstract: A marine bacterial strain, designated OB44-3T, was isolated from a crude oil-contaminated seawater sample collected near Dalian Bay, China. Cells of strain OB44-3T were Gramnegative, aerobic, rod-shaped, and oxidase- and catalasepositive. The major fatty acids were branched-chain saturated iso-C15:0 (27.9%) and unsaturated iso-C17:1 ω9c (14.8%). The DNA G+C content was 64.6 mol%. Phylogenetic analysis based on the 16S rRNA gene sequence indicated that strain OB44-3T was a member of the genus Luteimonas (95–96% 16S rRNA gene sequence similarity); its closest neighbors were the type strains of Luteimonas terricola (96% sequence similarity), Luteimonas mephitis (96%), and Luteimonas lutimaris (96%). On the basis of phenotypic, chemotaxonomic, and phylogenetic distinctiveness, strain OB44-3T was considered to represent a novel species of the genus Luteimonas. The name Luteimonas dalianensis sp. nov. is proposed, with strain OB44-3T (=CGMCC 1.12191T =JCM 18136T) as the type strain.

Inhibitory Effects of 4-Hydroxy-2,5-Dimethyl-3(2H)-Furanone (HDMF) on Acyl-Homoserine Lactone-Mediated Virulence Factor Production and Biofilm Formation in Pseudomonas aeruginosa PAO1: Sung-Chan Choi , Can Zhang , Sooyoung Moon , Young-Sook Oh; J. Microbiol. 2014;52(9):734-742. Published online August 2, 2014; DOI: https://doi.org/10.1007/s12275-014-4060-x

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22 Citations

Abstract: 4-Hydroxy-2,5-dimethyl-3(2H)-furanone (HDMF), a nonhalogenated furanone found in a variety of fruits, has been shown to have antimicrobial activity. However, few studies have focused on its inhibitory effect on bacterial quorum sensing (QS) at levels below the non-inhibitory concentration. In this study, 0.1 μM HDMF decreased the production of QS signal molecules and inhibited QS-controlled biofilm formation by Pseudomonas aeruginosa PAO1 without causing growth inhibition. In the presence of 0.1 and 1.0 μM HDMF, biofilm production by PAO1 was reduced by 27.8 and 42.6%, respectively, compared to that by untreated control cells. HDMF (1.0 μM) also significantly affected virulence factor expression (regulated by the las, rhl, and pqs system), resulting in a significant reduction in the production of LasA protease (53.8%), rhamnolipid (40.9%), and pyocyanin (51.4%). This HDMF-dependent inhibition of virulence factor expression was overcome by increasing the levels of two QS signal molecules of P. aeruginosa, N-(3-oxo-dodecanoyl)-L-homoserine lactone and N-butyryl-L-homoserine lactone, suggesting reversible competitive inhibition between HDMF and these molecules. The results of this study indicate that HDMF has great potential as an inhibitor of QS, and that it may be of value as a therapeutic agent and in biofilm control, without increasing selective pressure for resistance development.

Phosphorylation Regulates Mycobacterial Proteasome: Tripti Anandan , Jaeil Han , Heather Baun , Seeta Nyayapathy , Jacob T. Brown , Rebekah L. Dial , Juan A. Moltalvo , Min-Seon Kim , Seung Hwan Yang , Donald R. Ronning , Robert N. Husson , Joowon Suh , Choong-Min Kang; J. Microbiol. 2014;52(9):743-754. Published online September 2, 2014; DOI: https://doi.org/10.1007/s12275-014-4416-2

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17 Citations

Abstract: Mycobacterium tuberculosis possesses a proteasome system that is required for the microbe to resist elimination by the host immune system. Despite the importance of the proteasome in the pathogenesis of tuberculosis, the molecular mechanisms by which proteasome activity is controlled remain largely unknown. Here, we demonstrate that the α-subunit (PrcA) of the M. tuberculosis proteasome is phosphorylated by the PknB kinase at three threonine residues (T84, T202, and T178) in a sequential manner. Furthermore, the proteasome with phosphorylated PrcA enhances the degradation of Ino1, a known proteasomal substrate, suggesting that PknB regulates the proteolytic activity of the proteasome. Previous studies showed that depletion of the proteasome and the proteasome- associated proteins decreases resistance to reactive nitrogen intermediates (RNIs) but increases resistance to hydrogen peroxide (H2O2). Here we show that PknA phosphorylation of unprocessed proteasome β-subunit (pre-PrcB) and α-subunit reduces the assembly of the proteasome complex and thereby enhances the mycobacterial resistance to H2O2 and that H2O2 stress diminishes the formation of the proteasome complex in a PknA-dependent manner. These findings indicate that phosphorylation of the M. tuberculosis proteasome not only modulates proteolytic activity of the proteasome, but also affects the proteasome complex formation contributing to the survival of M. tuberculosis under oxidative stress conditions.

Enhanced Production of Carboxymethylcellulase by a Marine Bacterium, Bacillus velezensis A-68, by Using Rice Hulls in Pilot-scale Bioreactor under Optimized Conditions for Dissolved Oxygen: Wa Gao , Hye-Jin Kim , Chung-Han Chung , Jin-Woo Lee; J. Microbiol. 2014;52(9):755-761. Published online July 30, 2014; DOI: https://doi.org/10.1007/s12275-014-4156-3

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11 Citations

Abstract: The optimal conditions for the production of carboxymethylcellulase (CMCase) by Bacillus velezensis A-68 at a flask scale have been previously reported. In this study, the parameters involved in dissolved oxygen in 7 and 100 L bioreactors were optimized for the pilot-scale production of CMCase. The optimal agitation speed and aeration rate for cell growth of B. velezensis A-68 were 323 rpm and 1.46 vvm in a 7 L bioreactor, whereas those for the production of CMCase were 380 rpm and 0.54 vvm, respectively. The analysis of variance (ANOVA) implied that the highly significant factor for cell growth was the aeration rate, whereas that for the production of CMCase was the agitation speed. The optimal inner pressures for cell growth and the production of CMCase by B. velezensis A-68 in a 100 L bioreactor were 0.00 and 0.04 MPa, respectively. The maximal production of CMCase in a 100 L bioreactor under optimized conditions using rice hulls was 108.1 U/ml, which was 1.8 times higher than that at a flask scale under previously optimized conditions.

Novel Mutations in CYP51B from Penicillium digitatum Involved in Prochloraz Resistance: Jinlong Wang , Jinhui Yu , Jing Liu , Yongze Yuan , Na Li , Muqing He , Ting Qi , Geng Hui , Li Xiong , Deli Liu; J. Microbiol. 2014;52(9):762-770. Published online August 2, 2014; DOI: https://doi.org/10.1007/s12275-014-4112-2

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46 Citations

Abstract: Green mold caused by Penicillium digitatum is one of the most serious postharvest diseases of citrus fruit, and it is ubiquitous in all citrus growing regions in the world. Sterol 14α-demethylase (CYP51) is one of the key enzymes of sterol biosynthesis in the biological kingdom and a prime target of antifungal drugs. Mutations in CYP51s have been found to be correlated with resistance to azole fungicides in many fungal species. To investigate the mechanism of resistance to prochloraz (PRC) in P. digitatum, the PRC sensitivity was determined in vitro in this study to assess the sensitivity of 78 P. digitatum isolates collected in Hubei province. The results showed that 25 isolates were prochloraz-resistant (PRC-R), including six high-resistant (HR) strains, twelve medium-resistant (MR) and seven low-resistant (LR) strains. A sequence analysis showed no consistent point mutations of PdCYP51A in the PRC-R strains, but four substitutions of CYP51B were found, Q309H in LR strains, Y136H and Q309H in HR strains, and G459S and F506I in MR strains, which corresponded to the four sensitivity levels. Based on the sequence alignment analysis and homology modeling followed by the molecular docking of the PdCYP51B protein, the potential correlation between the mutations and PRC resistance is proposed.

Pseudomonas aeruginosa MdaB and WrbA are Water-soluble Two-electron Quinone Oxidoreductases with the Potential to Defend against Oxidative Stress: Laura K Green , Anne C La Flamme , David F Ackerley; J. Microbiol. 2014;52(9):771-777. Published online August 2, 2014; DOI: https://doi.org/10.1007/s12275-014-4208-8

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20 Citations

Abstract: Water-soluble quinone oxidoreductases capable of reducing quinone substrates via a concerted two-electron mechanism have been implicated in bacterial antioxidant defence. Twoelectron transfer avoids formation of dangerously reactive semi-quinone intermediates, moreover previous work in Pseudomonas putida indicated a direct protective effect for the quinols generated by an over-expressed oxidoreductase. Here, the Pseudomonas aeruginosa orthologs of five quinone oxidoreductases – MdaB, ChrR, WrbA, NfsB, and NQO1 – were tested for their possible role in defending P. aeruginosa against H2O2 challenge. In in vitro assays, each enzyme was shown to reduce quinone substrates with only minimal semiquinone formation. However, when each was individually over-expressed in P. aeruginosa no overt H2O2-protective phenotype was observed. It was shown that this was due to a masking effect of the P. aeruginosa catalase, KatA; in a katA mutant, H2O2 challenged strains over-expressing the WrbA and MdaB orthologs grew significantly better than the empty plasmid control. A growth advantage was also observed for H2O2 challenged P. putida strains over-expressing P. aeruginosa wrbA, mdaB or katA. Despite not conferring a growth advantage to wild type P. aeruginosa, it is possible that these quinone oxidoreductases defend against H2O2 toxicity at lower concentrations.

Two Rhizobacterial Strains, Individually and in Interactions with Rhizobium sp., Enhance Fusarial Wilt Control, Growth, and Yield in Pigeon Pea: Swarnalee Dutta , Pranjal Morang , Nishanth Kumar S , B.S. Dileep Kumar; J. Microbiol. 2014;52(9):778-784. Published online September 2, 2014; DOI: https://doi.org/10.1007/s12275-014-3496-3

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10 Citations

Abstract: A Pseudomonas aeruginosa strain, RRLJ 04, and a Bacillus cereus strain, BS 03, were tested both individually and in combination with a Rhizobium strain, RH 2, for their ability to enhance plant growth and nodulation in pigeon pea (Cajanus cajan L.) under gnotobiotic, greenhouse and field conditions. Both of the rhizobacterial strains exhibited a positive effect on growth in terms of shoot height, root length, fresh and dry weight, nodulation and yield over the non-treated control. Co-inoculation of seeds with these strains and Rhizobium RH 2 also reduced the number of wilted plants, when grown in soil infested with Fusarium udum. Gnotobiotic studies confirmed that the suppression of wilt disease was due to the presence of the respective PGPR strains. Seed bacterization with drug-marked mutants of RRLJ 04 and BS 03 confirmed their ability to colonize and multiply along the roots. The results suggest that co-inoculation of these strains with Rhizobium strain RH 2 can be further exploited for enhanced growth, nodulation and yield in addition to control of fusarial wilt in pigeon pea.

Antimicrobial Resistance, Virulence Genes and PFGE-profiling of Escherichia coli Isolates from South Korean Cattle Farms: Seung Won Shin , Jae-Won Byun , Myounghwan Jung , Min-Kyoung Shin , Han Sang Yoo; J. Microbiol. 2014;52(9):785-793. Published online July 30, 2014; DOI: https://doi.org/10.1007/s12275-014-4166-1

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13 Citations

Abstract: To estimate the prevalence of Escherichia coli with potential pathogenicity in cattle farm in South Korea, a total of 290 E. coli isolates were isolated from cattle farms over a period of 2 years in South Korea. These were examined for phenotypic and genotypic characteristics including antimicrobial susceptibility, serotype, and gene profiles of virulence and antimicrobial resistance. The most dominant virulence gene was f17 (26.2%), followed by stx2 (15.9%), ehxA (11.0%), stx1 (8.3%), eae (5.2%), and sta (4.1%). Some shiga-toxin producing E. coli isolates possessed eae (15.9%). All isolates except for one showed resistance to one or more antimicrobials, with 152 isolates exhibiting multidrug-resistance. The most prevalent resistance phenotype detected was streptomycin (63.1%), followed by tetracycline (54.5%), neomycin (40.3%), cephalothin (32.8%), amoxicillin (30.0%), ampicillin (29.7%), and sulphamethoxazole/trimethoprim (16.6%). The associated resistance determinants detected were strAstrB (39.0%), tet(E) (80.0%), tet(A) (27.6%), aac(3)-IV (33.1%), aphA1 (21.4%), blaTEM (23.8%), and sul2 (22.1%). When investigated by O serotyping and PFGE molecular subtyping, the high degree of diversity was exhibited in E. coli isolates. These results suggest that E. coli isolates from South Korean cattle farms are significantly diverse in terms of virulence and antimicrobial resistance. In conclusion, the gastroinstestinal flora of cattle could be a significant reservoir of diverse virulence and antimicrobial resistance determinants, which is potentially hazardous to public health.

Preliminary Study about Sublingual Administration of Bacteria-expressed Pandemic H1N1 Influenza Vaccine in Miniature Pigs: Hyekwon Kim , Jeong-Ki Kim , Hohyun Song , Jungah Choi , Byoungshik Shim , Bokyu Kang , Hyoungjoon Moon , Minjoo Yeom , Sang-Hyun Kim , Daesub Song , Manki Song; J. Microbiol. 2014;52(9):794-800. Published online July 30, 2014; DOI: https://doi.org/10.1007/s12275-014-4289-4

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Abstract: Sublingual (SL) administration of influenza vaccine would be non-invasive and effective way to give human populations protective immunity against the virus, especially when pandemic influenza outbreaks. In this study, the efficacy of pandemic influenza virus-based subunit vaccines was tested after sublingual (SL) adjuvant administration in pigs. Eight specific pathogen-free Yucatan pigs were divided into 4 groups: nonvaccinated but challenged (A) and vaccinated and challenged (B, C, and D). The vaccinated groups were subdivided by vaccine type and inoculation route: SL subunit vaccine (hemagglutinin antigen 1 [HA1] + wild-type cholera toxin [wtCT], B); IM subunit vaccine (HA1 + aluminum hydroxide, C); and IM inactivated vaccine (+ aluminum hydroxide, D). The vaccines were administered twice at a 2-week interval. All pigs were challenged with pandemic influenza virus (A/swine/ GCVP-KS01/2009 [H1N1]) and monitored for clinical signs, serology, viral shedding, and histopathology. After vaccination, hemagglutination inhibition titre was higher in group D (320) than in the other vaccinated groups (40–80) at the time of challenge. The mobility and feed intake were reduced in group C. Both viral shedding and histopathological lesions were reduced in groups B and D. Although this study has limitation due to the limited number of pigs (2 pigs per a group), the preliminary data in this study provided the protective potential of SL administration of bacteria-expressed pandemic H1N1 influenza vaccine in pigs. There should be additional animal studies about effective adjuvant system and vaccine types for the use of SL influenza vaccination.

NOTE] Is The Biotransformation of Chlorinated Dibenzo-p-dioxins by Sphingomonas wittichii RW1 Governed by Thermodynamic Factors?: In-Hyun Nam , Hyo-Bong Hong , Stefan Schmidt; J. Microbiol. 2014;52(9):801-804. Published online February 17, 2014; DOI: https://doi.org/10.1007/s12275-014-3424-6

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Abstract: Density functional theory (DFT) calculations were used to explore the relationship between the biotransformation of dibenzo-p-dioxin and selected chlorinated derivatives by resting cells of Sphingomonas wittichii RW1 and measuring the thermodynamic properties of the biotransformation substrates. Sphingomonas wittichii RW1 can aerobically catabolize dibenzo-p-dioxin as well as 2,7-dichloro-, 1,2,3-trichloro-, 1,2,3,4-tetrachloro-, and 1,2,3,4,7,8-hexachlorodibenzo-pdioxin; however, neither the 2,3,7-trichloro- nor the 1,2,3,7,8-pentachlorodibenzo-p-dioxin was transformed to its corresponding metabolic intermediate. The experimental biotransformation rates established were apparently governed by the selected thermodynamic properties of the substrates tested.

Author's Correction] Assessment of Microbial Diversity Bias Associated with Soil Heterogeneity and Sequencing Resolution in Pyrosequencing Analyses: Sokhee P. Jung , Hojeong Kang; J. Microbiol. 2014;52(9):805-805.; DOI: https://doi.org/10.1007/s12275-014-0703-1

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Abstract: In the article by Jung et al. published in Journal of Microbiology 2014; 52, 574-580. Acknowledgement should appear as shown below.

The authors thank In-Seon Son (ChunLab, Inc.) for her assistance in bioinformatics. This research was supported by the National Research Foundation of Korea (# 2013056833). H. Kang is grateful to ERC (2013067218).

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