Biological and molecular characterization of a bacteriophage infecting Xanthomonas campestris pv. campestris, isolated from brassica fields.

Xanthomonas campestris pv. campestris (Xcc) is the causal agent of black rot of crucifers. Here, we report a virus that infects Xcc isolated from brassica fields in Brazil. Morphological, molecular and phylogenetic analysis indicated that the isolated virus is a new member of the genus Pbunavirus, family Myoviridae, and we propose the name "Xanthomonas virus XC 2" for this virus. The isolated virus has a narrow host range, infecting only Xcc isolates, and it did not infect unrelated bacteria. These results indicate that the isolated bacteriophage is highly specific for Xcc and may be a potential agent for biological control.

Pan Proteome of Xanthomonas campestris pv. campestris Isolates Contrasting in Virulence.

Fully sequenced genomes of Xanthomonas campestris pv. campestris (Xcc) strains are reported. However, intra-pathovar differences are still intriguing and far from clear. In this work, the contrasting virulence between two isolates of Xcc - Xcc51 (more virulent) and XccY21 (less virulent) is evaluated by determining their pan proteome profiles. The bacteria are grown in NYG and XVM1 (optimal for induction of hrp regulon) broths and collected at the max-exponential growth phase. Shotgun proteomics reveals a total of 329 proteins when Xcc isolates are grown in XVM1. A comparison of both profiles reveals 47 proteins with significant abundance fluctuations, out of which, 39 show an increased abundance in Xcc51 and are mainly involved in virulence/adaptation mechanisms, genetic information processing, and membrane receptor/iron transport systems, such as BfeA, BtuB, Cap, Clp, Dcp, FyuA, GroEs, HpaG, Tig, and OmpP6. Several differential proteins are further analyzed by qRT-PCR, which reveals a similar expression pattern to the protein abundance. The data shed light on the complex Xcc pathogenicity mechanisms and point out a set of proteins related to the higher virulence of Xcc51. This information is essential for the development of more efficient strategies aiming at the control of black rot disease.

Antagonism of Yeasts to Xanthomonas Campestris PV. Campestris on Cabbage Phylloplane in field

Twenty yeast isolates, obtained from cabbage phylloplane, were evaluated for antagonistic activity against Xanthomonas campestris pv. campestris, in field. Plants of cabbage ev. Midori were pulverized simultaneously with suspensions of antagonists and pathogen. After 10 days, plants were evaluated through percentage of foliar area with lesions. Percentage of disease severity reduction (DSR per cent) was also calculated. Yeast isolates LR32, LR42 and LR19 showed, respectively, 72, 75 and 79 (per cent) of DSR. These antagonists were tested in seven different application periods in relation to pathogen inoculation (T1=4 d before; T2=simultaneously; T3=4 d after; T4=4 d before + simultaneously; T5=4 d after + simultaneously; T6=4 d before + 4 d after; T7=4 d before + simultaneously + 4 d after). The highest DSRs were showed by LR42 (71 per cent), LR42 (67 per cent), LR35 (69 per cent) and LR19 (68 per cent) in the treatments T7, T4, T5, and T6, which significantly differed from the others. The same yeast antagonists were also tested for back rot control using different cabbage cultivars (Fuyutoyo, Master-325, Matsukaze, Midori, Sekai I and Red Winner). The DSRs varied from 58 to 61 (per cent), and there was no significant difference among cultivars

Xanthan Production by Xanthomonas campestris in a whey-based medium

Isodados de Xanthomonas campestris foram adaptados à utilizaçäo de lactose para produçäo de xantana. Um meio mínimo de soro de leite (sem desproteinizaçäo e hidrólise) foi desenvolvido contendo 0,5 por cento K2HPO4; 0,01 por cento MgSO4 e 4 por cento leite gerando 14Kg/10 de goma. A viscosidade de soluçöes das gomas obtidas pelos isolados também foi avaliada

[Bacterial leaf blight affecting Syngonium podophyllum in Argentina]. / Tizón bacteriano de Syngonium podophyllum en la Argentina.

Bacterial leaf blight of Syngonium podophyllum caused by Xanthomonas campestris pv. syngonii is recorded for the first time in Argentina. The first symptom of the disease was an interveinal watersoaking of leaves, the tissues became chlorotic and finally necrotic over areas of about 4 cm. The identification of the causal microorganism was based on disease symptoms, morphological, physiological and biochemical characteristics and pathogenicity test.

Producción de gomas xánticas / Production of xanthan gums

En el período que va desde febrero has agosto de 1990, se realizó un relevamiento de Xanthomonas campestris en la zona de Luján, provincia de Buenos Aires, de 70 muestras de vegetales infectados. Se comprobó si las 50 cepas de Xanthomonas campestris obtenidas presentaban la capacidad de producir goma xantan, así como el porcentaje de conversión de sustrato en goma y el recuento de Xanthomonas campestris viables/ml de cultivo. Los mayores números de cepas productoras del polisacárido extracelular se obtuvieron de alfalfa. Asimismo, la Xanthomonas campestris pv. alfalfae presentó elevados números de células viables y porcentajes de conversión de glucosa en goma xántica

Producción de gomas xánticas / Production of xanthan gums

En el período que va desde febrero has agosto de 1990, se realizó un relevamiento de Xanthomonas campestris en la zona de Luján, provincia de Buenos Aires, de 70 muestras de vegetales infectados. Se comprobó si las 50 cepas de Xanthomonas campestris obtenidas presentaban la capacidad de producir goma xantan, así como el porcentaje de conversión de sustrato en goma y el recuento de Xanthomonas campestris viables/ml de cultivo. Los mayores números de cepas productoras del polisacárido extracelular se obtuvieron de alfalfa. Asimismo, la Xanthomonas campestris pv. alfalfae presentó elevados números de células viables y porcentajes de conversión de glucosa en goma xántica (AU)

[Production of xanthan gums]. / Producción de gomas xánticas.

Xanthomonas campestris was investigated in 70 samples of infected plants in the neighbourhood of Luján, province of Buenos Aires, between February and August, 1990. The production of xanthan gum was determined from 50 strains of Xanthomonas campestris, as well as the conversion efficiency of substrate concentration into gum and the number of colony forming units (CFU) of Xanthomonas campestris/ml of broth culture. The highest number of strains producing extracellular polysaccharide was obtained from alfalfa. Xanthomonas campestris pv. alfalfa gave elevated cell concentration and conversion efficiency of glucose in xanthan gum.