Watch out! It loves parasitic relationships...

Xanthomonas campestris (Xcc) is a commonly known plant pathogen that causes vascular disease, universally known as black rot.  It affects crucifers such as Brassica and Arabidopsis, which are particular organisms related to the cabbage and mustards.  It can attack the plants at any time during their life cycle; time of infection mainly depends on the environmental conditions.  The bacterium infects the plant via leaf pores, injuries to the plant’s leaves, or through its roots.  The most common way of infection for the bacterial phytopathogen is to use hydathodes, commonly through the most abundant pore on the leaf surface, stomata.  Infection thrives in warm, wet weather and increase transimission from plant to plant through exposing selves to extreme moist environments, windblown droplets, and transmission by humans and other animals.

                                                           

                   

Once infected the crucifers express symptoms beginning with the yellowing of edge of the leaf, which as the disease persists the marginal leaf chlorosis continues forming the characteristic "V”-shaped lesion.  Veins within the vascular tissue begin to darken as the disease becomes systemic.  In its advanced stages, the disease causes full leaf chlorosis, wilting, and eventually necrosis.

                                        

This parasitic relationship that Xcc exhibits with a wide range of crucifers is also known to infect weeds, including Arabidopsis thaliana.  Through the basis of this interaction, both Xcc and Arabidopsis thaliana’s genomes have been sequenced and are recently being used as model species used in current plant research.

                                                 

Xanthomonas campestris is identified as a chemoorganotroph, which is known to get their majority of energy from oxidizing organic compound commonly obtained from their host’s sugars, fats and proteins.  Xcc is known to be involved in a parasitic interaction with plants, more precisely crucifers, allowing them to obtain these organic compounds from the host plant.  In order to acquire energy from the obtained sugars, fats and proteins Xcc has to use oxygen to oxidize these substrates which classify Xcc as an obligate aerobe.  An obligate aerobic lifestyle is a common prokaryotic metabolism in which oxygen is in high demand and needed for these organisms, such as Xcc to properly undergo cellular respiration.  The oxygen that is required is used as the terminal electron acceptor for the aerobic respiration process.  The use of the Entener-Doudoroff pathway is the main pathway used to catalyze glucose to aid in fulfilling the high demand of energy that Xcc has.  Another organism that uses this type of metabolism is Escherichia coli.

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Now that we know where Xcc gets its grub from, it's important to check out the aid that it and its components hold in human food production.

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