First Report of a Leaf Blight, Seed Stalk Rot, and Bulb Decay of Onion by Pantoea ananas in Georgia

In May 1997, sweet onions (Allium cepa L.) grown in Toombs County, GA, displayed symptoms of blighted leaves, bleached and rotted seed stalks, and rotted bulbs. Gram-negative bacteria were isolated from infected tissues on nutrient agar and shown to be from the genus Pantoea on the basis of cell morphology (rod-shaped), yellow pigmentation, utilization of glucose in an oxidative and fermentative manner, presence of catalase, and absence of oxidase. These characteristics are typical of bacterial strains belonging to the Enterobacteriaceae (facultative anaerobes). Initially, these bacteria were thought to be P. agglomerans, a common saprophyte associated with plant material. However, fatty acid analysis, using bacterial identification software (MIDI, Dewark, DE), identified (second choice) some strains as possibly being P. ananas.. Further testing indicated that all strains utilized cellobiose, melibiose, inositol, glycerol, and sucrose, but not pectin, starch, or gelatin. However, those strains identified by fatty acid analysis as P. ananas were differentiated from P. agglomerans on the basis of indole production, lack of phenylalanine deaminase, and lack of nitrate reductase. To confirm pathogenicity, three strains of each species (total of six strains) were grown overnight in nutrient broth shake cultures. Bacterial cells were harvested by centrifugation and suspended in 0.01 M phosphate-buffered saline (0.85%). Inoculum was adjusted to approximately 5 × 108 CFU/ml with a spectrophotometer and misted with a chromatography sprayer onto onion leaves of approximately 10-week-old onion plants in the greenhouse. Onions were predisposed by placing them under plastic bags for 18 h prior to inoculation. Inoculated plants were left covered with plastic bags for an additional 24 h after inoculation. There were two plants per pot, each test had three pots, and the test was conducted twice. The three strains of P. agglomerans and buffer control resulted in no symptoms. The three strains of P. ananas produced severe blighting, rapid collapse of tissues, and rapid drying so that leaves were light tan and dry within 3 days. Disease on plants infected with P. ananas continued to develop until death of all foliage and bulbs shriveled and collapsed. Results were consistent for all replications and both trials. Bacteria recovered from diseased tissues were gram-negative, yellow, and facultative anaerobic, and produced indole but not phenylalanine deaminase or nitrate reductase; i.e., the bacteria demonstrated the same characteristics as P. ananas. Although P. agglomerans has been reported to produce similar symptoms in South Africa (1), our P. agglomerans strains were nonpathogenic. To our knowledge this is the first report of P. ananas causing a disease of onion. Reference: (1) M. J. Hattingh and D. F. Walters Plant Dis. 65:615, 1981.

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Diversity of culturable heterotrophic aerobic bacteria in pristine stream bed sediments

Canadian Journal of Microbiology ◽

10.1139/w99-081 ◽

1999 ◽

Vol 45 (10) ◽

pp. 879-884 ◽

Cited By ~ 13

Author(s):

L Halda-Alija ◽

T C Johnston

Keyword(s):

Fatty Acid ◽

Restriction Analysis ◽

Fatty Acid Analysis ◽

Aerobic Bacteria ◽

Gram Negative Bacteria ◽

Bed Sediments ◽

Gram Negative ◽

Gram Positive Bacteria ◽

Genotypic Analysis ◽

Dna Restriction

More than 900 culturable, heterotrophic aerobic isolates were obtained from the sediments of a forested, pristine stream and analyzed using three classical microbiological tests: API 20E, amplified ribosomal DNA restriction analysis (ARDRA), and fatty acid analysis. Gram-negative bacteria comprised most of the heterotrophic aerobic isolates (66.7%), similar to other oligotrophic environments. The isolates were assigned to the genus level as Pseudomonas, Flavobacterium, Micrococcus, Bacillus, Chromobacterium, Acinetobacter, Alcaligenes, Aeromonas, Methylobacterium, Enterobacter, Corynebacterium, and Sporolactobacillus. Genotypic analysis by ARDRA facilitated the comparison among strains within Pseudomonas, Bacillus, and Enterobacter groups. Temperature and predation may influence the survival of bacteria during seasons, as shown previously by others. Our results showed that the number of heterotrophic aerobic bacteria, especially Enterobacter, Alcaligenes, and Aeromonas, and Gram-positive bacteria, decreased in winter compared to summer conditions.Key words: stream, heterotrophic aerobic bacteria, ARDRA.

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Endotoxin Activity of Moraxella osloensis against the Grey Garden Slug, Deroceras reticulatum

Applied and Environmental Microbiology ◽

10.1128/aem.68.8.3943-3947.2002 ◽

2002 ◽

Vol 68 (8) ◽

pp. 3943-3947 ◽

Cited By ~ 24

Author(s):

Li Tan ◽

Parwinder S. Grewal

Keyword(s):

Biological Control ◽

Parasitic Nematode ◽

Lethal Dose ◽

Bacterial Cells ◽

Negative Bacterium ◽

Deroceras Reticulatum ◽

Gram Negative ◽

First Report ◽

Moraxella Osloensis ◽

Endotoxin Activity

ABSTRACT Moraxella osloensis is a gram-negative bacterium associated with Phasmarhabditis hermaphrodita, a slug-parasitic nematode that has prospects for biological control of mollusk pests, especially the grey garden slug, Deroceras reticulatum. This bacterium-feeding nematode acts as a vector that transports M. osloensis into the shell cavity of the slug, and the bacterium is the killing agent in the nematode-bacterium complex. We discovered that M. osloensis produces an endotoxin(s), which is tolerant to heat and protease treatments and kills the slug after injection into the shell cavity. Washed or broken cells treated with penicillin and streptomycin from 3-day M. osloensis cultures were more pathogenic than similar cells from 2-day M. osloensis cultures. However, heat and protease treatments and 2 days of storage at 22°C increased the endotoxin activity of the young broken cells but not the endotoxin activity of the young washed cells treated with the antibiotics. This suggests that there may be a proteinaceous substance(s) that is structurally associated with the endotoxin(s) and masks its toxicity in the young bacterial cells. Moreover, 2 days of storage of the young washed bacterial cells at 22°C enhanced their endotoxin activity if they were not treated with the antibiotics. Furthermore, purified lipopolysaccharide (LPS) from the 3-day M. osloensis cultures was toxic to slugs, with an estimated 50% lethal dose of 48 μg per slug, thus demonstrating that the LPS of M. osloensis is an endotoxin that is active against D. reticulatum. This appears to be the first report of a biological toxin that is active against mollusks.

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First Report of Acidovorax avenae subsp. avenae Causing Bacterial Leaf Stripe of Strelitzia nicolai

Plant Disease ◽

10.1094/pdis-03-11-0160 ◽

2011 ◽

Vol 95 (11) ◽

pp. 1474-1474 ◽

Cited By ~ 2

Author(s):

T. E. Seijo ◽

N. A. Peres

Keyword(s):

Pathogenic Bacteria ◽

Fatty Acid Analysis ◽

South Florida ◽

Metabolic Phenotype ◽

Bacterial Suspension ◽

Rrna Gene ◽

First Report ◽

Plastic Bags ◽

Young Leaves ◽

Symptomatic Tissue

White bird of paradise (Strelitzia nicolai Regel & K. Koch) is a commonly grown ornamental in central and south Florida. Each summer of 2004 to 2007, a reoccurring disease was observed at a commercial nursery in central Florida. Diseased plants had brown, necrotic stripes between the lateral leaf veins, which usually appeared along the midvein and spread toward the leaf edge. Lesions developed on the youngest leaves as they emerged from the central whorl. During 2004 and 2005, 20 symptomatic leaves were sampled. A white, nonfluorescent bacterium was consistently isolated from symptomatic tissue. It induced a hypersensitive response (HR) on tomato, grew at 41°C, and was identified as a Acidovorax sp. based on fatty acid analysis and as Acidovorax avenae subsp. avenae by Biolog metabolic phenotype analysis (similarity 0.76 to 0.86). A partial 16S rRNA gene sequence (1,455 bp) (Accession No. EF418616) was identical to four sequences in the NCBI (National Center for Biotechnology Information) database: one from A. avenae subsp. avenae and three from A. avenae of undetermined subspecies. To confirm pathogenicity, a bacterial suspension (O.D590 = 0.1) was applied to fill the central whorl (~0.5 to 1 ml) of potted S. nicolai. Plants were incubated for 7 to 10 days inside plastic bags at ambient temperature. Plants were inoculated individually with five strains of A. avenae subsp. avenae, four from S. nicolai, and one from corn (ATCC19860). Two to nine plants per strain were inoculated in each experiment. All strains were tested at least twice and noninoculated control plants were included. Symptoms were reproduced on the emerging leaf of 50 to 100% of inoculated plants with all five A. avenae subsp. avenae strains. No symptoms were observed on the controls. The bacteria recovered from symptomatic tissue were confirmed to be A. avenae subsp. avenae. Corn seedlings were inoculated as described above, except that entire seedlings were sprayed. Water-soaked lesions along the length of older leaf blades developed in 4 to 7 days. Only the corn strain was pathogenic (>80% of seedlings symptomatic), indicating host specificity. To our knowledge, this is the first report of A. avenae subsp. avenae infecting S. nicolai. In 1971, Wehlburg (2) described the same symptoms on orange bird of paradise (S. reginae) as being caused by a nonfluorescent Pseudomonas sp. This report likely describes the same disease since the published description is consistent with symptoms caused by A. avenae subsp. avenae. The pathogen reported by Wehlburg (2) had one polar flagellum, reduced nitrate, produced oxidase and a HR, and utilized arabinose, but not sucrose or arginine, characteristics consistent with those of A. avenae subsp. avenae (1). The only difference was A. avenae subsp. avenae has a delayed positive starch hydrolysis (1), whereas Welhburg's strain was negative. This disease occurs mainly on young leaves when plants receive daily overhead irrigation. Incidence can be as high as 40%, occasionally causing mortality, but even mild symptoms affect appearance and reduce marketability as an ornamental. References: (1) N. W. Schaad et al. Laboratory Guide for Identification of Plant Pathogenic Bacteria. 3rd ed. The American Phytopathological Society, St. Paul, MN, 2001. (2) C. Wehlburg. Plant Dis. Rep. 55:447, 1971.

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First report of isolation of antibacterial ceramides from the leaves of Euclinia longiflora Salisb

Natural Product Communications ◽

10.1177/1934578x211048628 ◽

2021 ◽

Vol 16 (11) ◽

pp. 1934578X2110486

Author(s):

Aristide Munvera ◽

Jean Noël Nyemb ◽

Tamfu Alfred Ngenge ◽

Marcelle Aude Fokam Mafo ◽

Shelha Nuzhat ◽

...

Keyword(s):

Fatty Acid ◽

Methanol Extract ◽

Methanolic Extract ◽

2D Nmr ◽

Antibacterial Activities ◽

Moderate Activity ◽

Bacterial Strains ◽

Maslinic Acid ◽

First Report ◽

Microdilution Method

Two phytosphingosine-type ceramides (euclinide A (1) and B (2)) were isolated alongside one fatty acid (geddic acid (3)), one fatty acid-1-glyceride ((2 S)-1- O-hentriacontanoyl glycerol (4)), ten triterpenes ( α-amyrin (5), α-amyrin acetate (6), ursolic acid (7), β-amyrin (8), β-amyrin acetate (9), β-amyrin palmitate (10), oleanic acid (11), maslinic acid (12), betulinic acid (13) and cylicodiscic acid (14)) and four sterols ( β -sitosterol (15), stigmasterol (17), and their glucosylated derivatives β-sitosterol-3-O- β-glucopyranoside (16) and stigmasterol-3-O- β-glucopyranoside (18)) from the methanol extract of the leaves of Euclinia longiflora Salisb. using routine chromatographic methods. The structures of the new ceramides and known compounds were determined by analyses of HR-FAB-MS, 1D and 2D NMR (HSQC, HMBC, and NOESY) data and confirmed, where applicable, by comparison with data reported in literature. The methanolic extract and the ceramides were evaluated for their antibacterial activities against different bacterial strains using microdilution method and the MIC values ranged from 6.25 to 50 μg/mL and were considered as moderate activity compared to ciprofloxacin. It is the first report of ceramides in Euclinia longiflora.

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Biocidal activity of chicken defensin-9 against microbial pathogens

Biochemistry and Cell Biology ◽

10.1139/bcb-2015-0121 ◽

2016 ◽

Vol 94 (2) ◽

pp. 176-187 ◽

Cited By ~ 10

Author(s):

Haitham A. Yacoub ◽

Salem M. El-Hamidy ◽

Maged M. Mahmoud ◽

Mohamed Nabih Baeshen ◽

Hussein A. Almehdar ◽

...

Keyword(s):

Candida Albicans ◽

Pathogenic Bacteria ◽

Sequence Similarity ◽

Expression Patterns ◽

Antimicrobial Activities ◽

Microbial Pathogens ◽

Bacterial Cells ◽

Bacterial Strains ◽

Gram Positive ◽

Gram Negative

In this study we identified the expression patterns of β-defensin-9 in chickens from Saudi Arabia, evaluated the antimicrobial activities of synthetic chicken β-defensin-9 (sAvBD-9) against pathogenic bacteria and fungi, and investigated the mode of action of sAvBD-9 on bacterial cells. The AvBD-9 gene of Saudi chickens encodes a polypeptide of 67 amino acids, which is highly similar to the polypeptide in duck, quail, and goose (97%, 86%, and 87%, respectively) and shares a low sequence similarity with the mammalian defensins. AvBD-9 is expressed in various organs and tissues of Saudi chickens and inhibits the growth of both Gram-negative and Gram-positive bacteria, as well as showing activity against unicellular and multicellular fungi (Aspergillus flavus, A. niger, and Candida albicans). sAvBD-9 completely inhibited the growth of both Gram-positive and Gram-negative bacterial strains as well as Candida albicans. The haemolytic effects of sAvBD-9 were limited. Morphological analysis by TEM revealed that sAvBD-9 induces shortening and swelling of Staphylococcus aureus and Shigella sonni cells, opens holes and deep craters in their envelopes, and leads to the release of their cytoplasmic content. Our data shed light on the potential applications of sAvBD-9 in the pharmaceutical industry.

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A New Water-Soluble Bactericidal Agent for the Treatment of Infections Caused by Gram-Positive and Gram-Negative Bacterial Strains

Antibiotics ◽

10.3390/antibiotics9090586 ◽

2020 ◽

Vol 9 (9) ◽

pp. 586

Author(s):

Alessandro Presentato ◽

Elena Piacenza ◽

Antonino Scurria ◽

Lorenzo Albanese ◽

Federica Zabini ◽

...

Keyword(s):

Water Soluble ◽

Hydrodynamic Cavitation ◽

Minimal Bactericidal Concentration ◽

Bacterial Cells ◽

Bacterial Strains ◽

Citrus Pectin ◽

Medical Treatments ◽

Gram Negative ◽

Log Reduction ◽

Citrus Flavonoids

Grapefruit and lemon pectin obtained from the respective waste citrus peels via hydrodynamic cavitation in water only are powerful, broad-scope antimicrobials against Gram-negative and -positive bacteria. Dubbed IntegroPectin, these pectic polymers functionalized with citrus flavonoids and terpenes show superior antimicrobial activity when compared to commercial citrus pectin. Similar to commercial pectin, lemon IntegroPectin determined ca. 3-log reduction in Staphylococcus aureus cells, while an enhanced activity of commercial citrus pectin was detected in the case of Pseudomonas aeruginosa cells with a minimal bactericidal concentration (MBC) of 15 mg mL−1. Although grapefruit and lemon IntegroPectin share equal MBC in the case of P. aeruginosa cells, grapefruit IntegroPectin shows boosted activity upon exposure of S. aureus cells with a 40 mg mL−1 biopolymer concentration affording complete killing of the bacterial cells. Insights into the mechanism of action of these biocompatible antimicrobials and their effect on bacterial cells, at the morphological level, were obtained indirectly through Fourier Transform Infrared spectroscopy and directly through scanning electron microscopy. In the era of antimicrobial resistance, these results are of great societal and sanitary relevance since citrus IntegroPectin biomaterials are also devoid of cytotoxic activity, as already shown for lemon IntegroPectin, opening the route to the development of new medical treatments of polymicrobial infections unlikely to develop drug resistance.

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First Report of Herbaspirillum rubrisubalbicans Causing Mottled Stripe Disease on Sugarcane in China

Plant Disease ◽

10.1094/pdis-94-3-0379b ◽

2010 ◽

Vol 94 (3) ◽

pp. 379-379 ◽

Cited By ~ 3

Author(s):

ZQ. Tan ◽

R. Men ◽

RY. Zhang ◽

Z. Huang

Keyword(s):

16S Rdna ◽

Uv Light ◽

Rdna Sequence ◽

Universal Primers ◽

Bacterial Cells ◽

Bacterial Strains ◽

Potato Dextrose Agar Medium ◽

16S Rdna Sequence ◽

First Report ◽

Herbaspirillum Rubrisubalbicans

Narrow, red stripes were observed on leaves and sheaths of sugarcane in 2007 in DanZhou County of Hainan Province and XuWen County of GuangDong Province, China. Stripes were parallel to the leaf veins. Some stripes were short (2 to 10 cm) and some were >1 m long, extending from the base of leaves. Width of the stripes was 2 to 4 mm. Symptoms varied with the cultivar. Cv. Taiwang 25, which was the most affected, exhibited red stripes and stalk death from the apex. Cvs. Taiwang 26 and Guang Dong 00236 were slightly affected with only red stripes. Symptoms on cv. Taiwang 22 were mottled stripes. Severe losses were observed in the infected fields that were planted with cv. Taiwang 25, but there were no obvious losses in fields planted with the other three cultivars. Isolations were made from 10 individual plants from different cultivars and provinces that had red stripes, two of which also had apex death. Five independent bacterial isolates were obtained from tissue showing the red stripe symptoms on potato dextrose agar medium. The percentage of positive samples was 50%. No bacteria were obtained from necrotic apex tissue. Bacterial cells were 0.92 to 1.55 × 0.20 to 0.22 μm slightly curved rods that were motile with one to two polar flagella. Colonies on nutrient agar were 2 to 3 mm in diameter, circular, smooth, entire, and milky white. Colonies on King's medium B were nonfluorescent under 365-nm UV light. Five bacterial strains were inoculated by injecting bacterial suspensions (1 × 108 CFU/ml) into the base of the leaves of 6-month-old cv. Taiwang 25 plants (1). Red stripes appeared 7 to 10 days after inoculation and bacteria were reisolated. The reisolated bacteria were identical to the original strains in colony morphology and 16S rDNA sequence. A hypersensitive response appeared within 24 h when 1 × 108 CFU/ml bacteria suspensions were infiltrated into tobacco leaves. Approximately 1,000-bp DNA fragments were amplified with universal primers UP1 (5′-TACGTGCCAGCAGCCGCGGTAATA-3′) and UP2 (5′-AGTAAGGAGGGTATCCAACCGCA-3′) (3). Primers UP1 and UP2 are complementary to nucleotide sequence 509 to 523 and 1541 to 1522, respectively, of the Escherichia coli 16S rDNA gene. The fragment amplified by these primers was approximately 1,032 bp. The 16S rDNA sequences of the five strains were deposited in GenBank as Accession Nos. GQ476791–5. They all shared 99% nucleotide identity with the type strain of Herbaspirillum rubrisubalbicans (GenBank No. AJ238356.1). All five strains were identified as H. rubrisubalbicans on the basis of 16S rDNA sequence and pathogenicity to sugarcane, and the disease was identified as mottled stripe disease (2). Since we were not able to isolate bacteria from necrotic apex tissue, this symptom on cv. Taiwang 25 may not be related to the H. rubrisubalbicans infection. To our knowledge, this is the first report of mottled stripe disease in China. References: (1) H. M. A. EI-Komy et al. Folia Microbiol. 48:787, 2003. (2) A. S. Saumtally et al. A Guide to Sugarcane Diseases. P. Rott et al., eds. CIRAD and ISSCT, Montpellier, France, 2000. (3) Yan Zhi Yong et al. Chin. J. Epidemiol. 24:296, 2003.

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First Report of Pink Seed of Pea Caused by Erwinia rhapontici in North Dakota

Plant Disease ◽

10.1094/pdis-92-2-0315a ◽

2008 ◽

Vol 92 (2) ◽

pp. 315-315 ◽

Cited By ~ 2

Author(s):

K. A. Wise ◽

Y. F. Zhao ◽

C. A. Bradley

Keyword(s):

Fatty Acid ◽

North Dakota ◽

The United States ◽

Fatty Acid Analysis ◽

Distilled Water ◽

Normal Appearance ◽

Bacterial Colony ◽

First Report ◽

Erwinia Rhapontici ◽

The University

In 2006, a seed lot of dry pea cv. DS Admiral obtained from Bowman County, North Dakota contained seed with bright-to-pale pink discoloration on the seed coat. Five discolored seeds and five seeds with normal appearance were surface disinfected in a 0.5% NaOCl solution for 1 min and rinsed with sterilized distilled water for 1 min. Seeds were placed onto potato dextrose agar (PDA) and incubated at 22°C. Three days later, the discolored seeds produced pink bacterial colonies and a pink pigment that diffused throughout the PDA. The pink bacterial colonies were tentatively identified as Erwinia rhapontici on the basis of colony and pigment color (2,3). No fungi or bacteria grew from the seed with normal appearance. A pink bacterial colony growing from one of the discolored seeds was streaked onto PDA and a single colony was obtained. A streaked plate incubated at 37°C showed no growth, which distinguishes E. rhapontici from Brenneria rubrifaciens (formerly E. rubrifaciens) (1–3). To confirm the identity, the isolate was sent to the Bacterial Identification and Fatty Acid Analysis Laboratory at the University of Florida, Gainesville. Fatty acid analysis indicated a similarity index of 0.515 for E. rhapontici. For an additional confirmation of identity, the 16S ribosomal DNA (rDNA) gene was amplified from the E. rhapontici isolate with universal primers fD1 and rP1 (4). The PCR product was cloned into pGEM-T easy vector (Promega, Madison, WI) and sequenced with primers SP6 and T7 at the Keck Biotechnology Center at the University of Illinois, Urbana. The resulting nucleotide sequence was compared with 16S rDNA sequences deposited in the ribosomal database ( http://rdp.cme.msu.edu/seqmatch/seqmatch_intro.jsp ) and showed highest identity to sequences of E. rhapontici or E. persicinus strains. To confirm pathogenicity, the basal ends of five pods on each of six pea plants (cv. Carneval) were syringe injected with 0.1 ml of suspension containing the obtained E. rhapontici isolate in the greenhouse by the methods as previously described (2). As a control, five pods on each of two plants were injected with 0.1 ml of sterile distilled water. Twenty-eight of the 51 seeds obtained from the bacteria-inoculated pods had pink seed symptoms, while seeds from the control pods appeared normal. Isolations from symptomatic and asymptomatic seed were performed as described above, and E. rhapontici was obtained from symptomatic seed. To our knowledge, this is the first report of pink seed of pea caused by E. rhapontici in North Dakota. The first report of this disease on pea in the United States was from Montana (3). References: (1) L. Hauben et al. Syst. Appl. Microbiol. 21:384, 1998. (2) H. C. Huang et al. Can. J. Plant Pathol. 12:445, 1990. (3) B. K. Schroeder et al. Plant Dis. 86:188, 2002. (4) W. G. Weisburg et al. J. Bacteriol. 173:697, 1991.

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Optical microscopy reveals the dynamic nature of B. pseudomallei morphology during β-lactam antimicrobial susceptibility testing

10.1101/2020.01.13.904995 ◽

2020 ◽

Author(s):

Heather P. McLaughlin ◽

Julia Bugrysheva ◽

David Sue

Keyword(s):

Optical Microscopy ◽

Antimicrobial Susceptibility ◽

Cell Morphology ◽

Morphological Changes ◽

Cell Lysis ◽

Bacterial Cells ◽

Bacterial Strains ◽

Gram Negative ◽

Resistant Strains ◽

Morphology Changes

AbstractBackgroundIn Gram-negative species, β-lactam antibiotics target penicillin binding proteins (PBPs) resulting in morphological alterations of bacterial cells. Observations of antibiotic-induced cell morphology changes can rapidly and accurately differentiate drug susceptible from resistant bacterial strains; however, resistant cells do not always remain unchanged. Burkholderia pseudomallei is a Gram-negative, biothreat pathogen and the causative agent of melioidosis, an often fatal infectious disease for humans.ResultsHere, we identified β-lactam targets in B. pseudomallei by in silico analysis. Ten genes encoding putative PBPs, including PBP-1, PBP-2, PBP-3 and PBP-6, were detected in the genomes of susceptible and resistant strains. Real-time, live-cell imaging of B. pseudomallei strains demonstrated dynamic morphological changes in broth containing clinically relevant β-lactam antibiotics. At sub-inhibitory concentrations of ceftazidime (CAZ), amoxicillin-clavulanic acid (AMC), and imipenem (IPM), filamentation, varying in length and proportion, was an initial response of the multidrug-resistant strain Bp1651 in exponential phase. However, a dominant morphotype reemerged during stationary phase that resembled cells unexposed to antibiotics. Similar morphology dynamics were observed for AMC-resistant strains, MSHR1655 and 724644, when exposed to sub-inhibitory concentrations of AMC. For all B. pseudomallei strains evaluated, increased exposure time and exposure to increased concentrations of AMC at and above minimal inhibitory concentrations (MICs) in broth resulted in cell morphology shifts from filaments to spheroplasts and/or cell lysis. B. pseudomallei morphology changes were more consistent in IPM. Spheroplast formation followed by cell lysis was observed for all strains in broth containing IPM at concentrations greater than or equal to MICs, however, the time to cell lysis was variable. Length of B. pseudomallei cells was strain-, drug- and drug concentration-dependent.ConclusionsBoth resistant and susceptible B. pseudomallei strains exhibited filamentation during early exposure to AMC and CAZ at concentrations used to interpret susceptibility (based on CLSI guidelines). While developing a rapid β-lactam antimicrobial susceptibility test based on cell-shape alone requires more extensive analyses, optical microscopy detected B. pseudomallei growth attributes that lend insight into antibiotic response and antibacterial mechanisms of action.

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First Report of Bacterial Spot of Lettuce Caused by Xanthomonas campestris pv. vitians in Turkey

Plant Disease ◽

10.1094/pdis.2000.84.4.490b ◽

2000 ◽

Vol 84 (4) ◽

pp. 490-490 ◽

Cited By ~ 12

Author(s):

F. Sahin

Keyword(s):

Leaf Spot ◽

Xanthomonas Campestris ◽

Fatty Acid Analysis ◽

Sterile Water ◽

Bacterial Strains ◽

Bacterial Leaf Spot ◽

First Report ◽

Black Water ◽

Pure Cultures ◽

Polyethylene Bags

During spring 1999, lettuce (Lactuca sativa) plants grown at Oltu in the eastern Anatolia region of Turkey were observed with numerous lesions typical of bacterial leaf spot. Lesions on leaves were irregular, small, pale green to black, water-soaked, and 2 to 5 mm in diameter. Coalescing lesions sometimes caused defoliation of older leaves. Isolations made from diseased leaves on yeast dextrose carbonate agar yielded nearly pure cultures of a yellow pigmented bacterium typical of a xanthomonad. Five bacterial strains were purified and used for further tests. The strains reacted positively with a Xanthomonas-specific monoclonal antibody, X1, in indirect enzyme-linked immunosorbent assays (1). Fatty acid analysis identified the strains as X. campestris pv. vitians (proposed name X. axonopodis pv. vitians), with greatest similarity indices of 29 to 71% (2). Pathogenicity of strains was confirmed on 5-week-old lettuce plants (cv. Darkland) sprayed with bacterial suspensions containing 108 CFU/ml of sterile water. Inoculated and sterile water-sprayed control plants were covered with polyethylene bags for 48 h at 25°C, after which bags were removed and plants were maintained in the greenhouse. Water-soaked spots similar to those in the field were observed on inoculated plants within 5 to 7 days. No symptoms developed on control plants. The bacterium was reisolated from inoculated plants and identified as X. campestris pv. vitians. This is the first report of bacterial leaf spot of lettuce in Turkey. References: (1) A. M. Alvarez et al. Phytopathology 84:1449, 1994. (2) Vauterin et al. Int. J. Syst. Bact. 45:472, 1995.

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