**7. Effect of** *Xanthobacter autotrophicus* **on the growth of** *Triticum aestivum* **and other domestic plants**

*Triticum aestivum* is the main cereal consumed by the human population of the world, around 51% of human demand intake of calories and proteins. The annual production of this crop is ~630 million tons, being the major grown cereal worldwide with ~740 million ha harvested annually [101]. It is reported that the dynamics of colonization of endophytic genus plant growth promoting bacteria (EPGPB) like *X. autotrophicus* on the sphermosphere/rhizosphere in gramineae is reported, based in other genera and species different than *Xanthobacter* [49, 102, 103]. In that sense the response of domestic plants to *X. autotrophicus* is scarce [18] so research in progress indicates [16, 17, 45, 46] that it may be an excellent option for the sustainable production of domestic crops [67, 104–106] however it is believed that it may be similar to other genera and species of EPGB, of the known like *Azospirillum, Azotobacter, Bacillus* which are able to move from outside to into the root system [18, 107]. In the case of *T. aestivum* has a positive response to *X. autotrophicus* since can invade the interior of the root system where it transforms organic compounds derived from photosynthesis into phytohormons, to optimize the reduced dose of nitrogen fertilizer [46]. It has been showed that can invade the root of *T. aestivum* including other types of domestic crops [17, 45, 60]. This biochemical characteristic of *X. autotrophicus* was confirmed by its growth dependent on the nutritional richness of the rhizosphere of *T. aestivum*, attributable to certain organic acids, amino acids including other organic compounds from the photosynthesis in gramineae [42, 108]. Hence, the importance of the chemical composition of root, sphermosphere and rhizosphere, as inducers of colonization by *X. autotrophycus* in gramineae, is key for other EPGPB to be closely associated with its root, sphermosphere, rhizosphere system [60, 105, 109]; in part this also explains the nutritional requirement of *X. autotrophicus* for wheat as a distinctive characteristic of this species, which is not reported in *X. autotrophicus* this was verified when was inoculated in the soil without roots, this coupled with the competition and predation of the native soil microorganisms, antagonistic to the species of *Xanthobacter*, which prevented its persistence in that environment [20, 47]. In the literature it is reported that the positive response of *T. aestivum* to inoculation with *X. autotrophicus* and fed with NH4NO3 depends on fast they colonized exclusively the germination zone of the seed, as well as to invade inside the roots when they have developed [41, 109, 110]. This explains why, in the case of the test described, *X. autotrophicus* was detected during seed germination, in the period of root development, and even inside mature roots of wheat. This suggests that *X. autotrophicus* was not dependent on wheat's sphermosphere/rhizosphere [17, 108, 109], it is reported that slowly used its energy reserve to prolong its persistence in unsterilized soil, a physiological characteristic in *X. autotrophicus* [111, 112]. These results support that *T. aestivum* were attractive for *X. autotrophicus* used according to the type of root growth observed with *T. aestivum*, compared to the appearance of the root system in the coronary part and by the density of secondary roots detected uninoculated wheat [37, 46, 47, 113, 114].

Related to phosphorus a key mineral for plant nutrition as phosphates normally applied to soil as fertilizer it is reported that concentration in average soils is about 0.05% (w/w) of which only 0.1% is available to plants [115]. There is evidence that the phosphate fertilizer applied as phosphate has a limited impact on plant nutrition, especially because, due to the solubilization constant (Ksp), of this phosphate anion is generally little available for plant roots [116]. It is calculated in the soil the concentration of phosphorus as phosphates is equal to or less than 0.02ppm, which drastically limits plant growth [117, 118]. In nature, the strategy that plants use for the absorption of the forms of phosphates necessary for plant metabolism are

Xanthobacter autotrophicus *an Endophytic Beneficial Bacterium for Wheat and Other Plants… DOI: http://dx.doi.org/10.5772/intechopen.102066*

#### **Figure 3.**

*Response of* Triticum aestivum *to* Xanthobacter autotrophicus *at different levels of nitrogen and phosphate fertilizer at seedling stage 30 days after sowing. (a) Absolute control:* T. aestivum *not inoculated irrigated only with water; (b) relative control:* T. aestivum *not inoculated fed at 100% nitrogen and phosphate fertilizer; (c)* T. aestivum *with* X. autotrophicus *fed with 50% of nitrogen fertilizer and 100% phosphate fertilizer; (d)* T. aestivum *with* X. autotrophicus *fed with 100% nitrogen fertilizer and 50% phosphate fertilizer; (e)* T. aestivum *with* X. autotrophicus *fed with 50% nitrogen and phosphate fertilizer*

the solubilization actions of phosphates by genera and species of microorganisms that promote plant growth, such as mycorrhizae and bacteria that also mineralize organic compounds containing phosphates [119, 120]. In the last few years, the development of microbial inoculum containing phosphate-solubilizing microbes (PSM) gained attention of agriculturists [17].

**Figure 3** shows the positive response of *T. aestivum* to *X. autotrophicus* fed at 50% of NH4NO3 and 100% phosphate fertilizer. **Figure 3c** shows that *T. aestivum* reached a greater number of leaves and a dense root system, as well as *T. aestivum* with *X. autotrophicus* fed with 100% nitrogen fertilizer and 50% phosphate fertilizer (**Figure 3d**) and *T. aestivum* with *X. autotrophicus* fed with 50% nitrogen and phosphate fertilizer (**Figure 3e**), compared to *T. aestivum* not inoculated irrigated with water (**Figure 3a**) and *T. aestivum* not inoculated fed with 100% nitrogen and phosphate fertilizer (**Figure 3b**). These facts indicates that *X. autotrophicus* transformed the organic compounds from photosynthesis of *T. aestivum* into root system to improve root absorption and optimize the reduced dose of nitrogen fertilizer without risk to plant health growth [17, 18, 38, 42, 43, 121, 122]. At the same time the synthesis of acid and mainly alkaline phosphatases improved the solubilization and absorption of soil phosphates and phosphate fertilizer apply [17, 123, 124] to enhance growth plant (data not showed). In **Figure 1** it was evident that *X. autotrophicus* is an excellent option for the sustainable production of *T. aestivum* since it is not only capable of optimizing nitrogen fertilizer to avoid soil deterioration and environmental contamination due to nitrogen hyperfertilization [36, 54, 121, 125, 126]. While *T. aestivum* inoculated with *X. autotrophicus* simultaneously absorbs the immobilized phosphate from the soil and optimizes the effective application from the inside of its roots by avoiding competition with the native microorganisms [13, 40, 53] with a high prognosis of achieving healthy growth and profitable yield [43, 122]. In that sense Khalid et al. [127] reported that seed inoculation with 30 bacterial strains isolated from rhizospheric soils of wheat plants cultivated at different sites significantly increased length and weight of wheat roots and shoots. Linear positive correlation between in vitro auxin production by these bacteria and increases in the measured growth parameters was observed. Abd El-Azeem et al. [128] reported a highly significant positive linear correlation between the in vitro auxin production by the tested PGPR strains and each of grain yield, straw and total yield (grain plus straw) as well as the number of tillers of wheat plants. Auxin or indole acetic acid (IAA) production is considered a way in which *X. autotrophicus* promotes plant growth by stimulating enzymological reactions [125, 129]. IAA influences plant processes, such as initiation of cell division and promotes vascular differentiation [130, 131]. Besides its hormonal functions, IAA is involved in the stimulation of ethylene synthesis, which is produced, by plants and microorganisms [47]. Ethylene plays several active roles in plants including germination of root and shoot and the response of plants to stress [43]. There is an evidence that *X. autotrophicus* that solubilize phosphate in soil and promote its uptake by plants are referred as phosphate solubilizing bacteria (PSB) or phosphobacteria and are included within EPGPB [132]. Plant growth promoting rhizobacteria increase the efficiency of fertilizers while reducing nitrogen loss. Their counts in the rhizosphere comprise a considerable share of the rhizospheric microorganisms and vary depending on the soil location and type as well as the cultivated plants [133]. Inoculating the soil or seeds with PSB individually or in combination with other microorganisms, especially the nitrogen-fixing bacteria increased the availability of P, Fe, Mn, Zn and Cu for plants and consequently increased crop yield [114, 134, 135].

**Figure 4** shows the positive response of *Z. mays* to *X. autotrophicus* fed with 50% nitrogen fertilizer and 100% phosphate fertilizer (**Figure 4c**), had the highest number of leaves, plant height and the highest root density, as well as *Z. mays* with *X. autotrophicus* fed with 100% nitrogen fertilizer and 50% phosphate fertilizer (**Figure 4d**) and *Z. mays* with *X. autotrophicus* fed with 50% nitrogen and phosphate fertilizer (**Figure 4e**), compared to *Z. mays* not inoculated irrigated only with water (**Figure 4a**) and *Z. mays* not inoculated fed with 100% nitrogen and phosphate fertilizer (**Figure 4b**). **Figure 2** shows the effect of *X. autotrophicus* on the healthy growth of *Z. mays* at different doses of nitrogen and phosphorous fertilizer, supporting that *X. autotrophicus* from the interior of the root system of *Z. mays* had the ability to convert compounds generated from photosynthesis in phytohormones for the optimization of the fertilizer reduced to 50%, simultaneously with an increase in the acid and alkaline phosphatase activity for the solubilization of the immobile phosphates of the soil and the optimization of the phosphate fertilizer also reduced 50% [17, 44, 45, 47, 106, 131] compared to the limited growth of *Z. mays* without inoculation with *X. autotrophicus* where the absence of this endophytic bacterium

#### **Figure 4.**

*Response of* Zea mays *to* Xanthobacter autotrophicus *at different levels of nitrogen and phosphate fertilizer at seedling stage 15 days after sowing. (a) absolute control:* Z. mays *not inoculated irrigated with water; (b) relative control:* Z. mays *not inoculated fed with 100% nitrogen and phosphate fertilizer; (c)* Z. mays *with* X. autotrophicus *fed with 50% nitrogen fertilizer and 100% phosphate fertilizer; (d)* Z. mays *with* X. autotrophicus *fed with 100% nitrogen fertilizer and 50% phosphate fertilizer; (e)* Z. mays *with*  X. autotrophicus *fed with 50% nitrogen and phosphate fertilizer.*

Xanthobacter autotrophicus *an Endophytic Beneficial Bacterium for Wheat and Other Plants… DOI: http://dx.doi.org/10.5772/intechopen.102066*

#### **Figure 5.**

*Positive response of* Oryza sativa *to* Xanthobacter autotrophicus *at different levels of nitrogen and phosphate fertilizer at seedling stage 15 days after sowing. (a) Absolute control:* O. sativa *not inoculated irrigated with water; (b) relative control:* O. sativa *not inoculated fed with 100% nitrogen and phosphate fertilizer; (c)* O. sativa *with* X. autotrophicus *fed with 50% nitrogen fertilizer and 100% phosphate fertilizer; (d)* O. sativa *with* X. autotrophicus *fed with 100% nitrogen fertilizer and 50% phosphate fertilizer; (e)* O. sativa *with* X. autotrophicus *fed with 50% nitrogen and phosphate fertilizer.*

that promotes plant growth shows that *Z. mays* that none of these fertilizers is efficiently absorbed, causing loss of soil fertility and a possible environmental contamination [43].

In **Figure 5**, showed the response of *O. sativa* to *X. autotrophicus* by the root length and plant height of *O. sativa* at 50% nitrogen fertilizer as NH4NO3 and 100% phosphorous fertilizer as K2HPO4/KH2PO4 (**Figure 5c**), in comparation to *O. sativa* with the maximum dose of nitrogen and phosphorous fertilizer but without *X. autotrophicus* (**Figure 5b**), as well as *O. sativa* with *X. autotrophicus* fed with 50% nitrogen and phosphate fertilizer (**Figure 5e**). This support that *X. autotrophicus* h is able to transform organic compounds from photosynthesis into phytohormons like auxins to increase root soil exploration for optimizing uptake of nitrogen fertilizer reduced to 50% [18, 45, 46, 106]. There is evidence that to support that *X. autotrophicus* in wheat, as well as in, oats, corn, sorghum, and other types of plants the way do other genus and species of growth plant promoting bacteria. While inside the roots of *O. sativa*; *X. autotrophicus* synthesizes acid and alkaline phosphatases for the solubilization and absorption of insoluble phosphate from the soil, as well as optimizing the phosphate fertilizer applied to the soil at a reduced dose without affecting the healthy growth of *O. sativa* compared to the response of *O. sativa* without inoculating with *X. autotrophicus* fed with the recommended dose of nitrogen and phosphate fertilizer, which shows that without the help of *X. autotrophicus*, *O. sativa* has growth limitations, therefore it is advisable to apply it to the sowing of the seed [119, 120, 123, 124, 126]. While inside the roots of *O. sativa*; *X. autotrophicus* synthesizes acid and alkaline phosphatases for the solubilization and absorption of insoluble phosphate from the soil, as well as optimizing the phosphate fertilizer applied to the soil at a reduced dose without affecting the healthy growth of *O. sativa* compared to the response of *O. sativa* without inoculating with *X. autotrophicus* fed with the recommended dose of nitrogen and phosphate fertilizer, which shows that without the help of *X. autotrophicus*; *O. sativa* has growth limitations, therefore it is advisable to apply it to the sowing of the seed [46, 106, 136].

In **Figure 6**, *L. sativa* inoculated with *X. autotrophicus* fed with 25% nitrogen and phosphate fertilizer (**Figure 6e**), as well as *L. sativa* with *X. autotrophicus* fed with 25% nitrogen fertilizer and 100% phosphate fertilizer (**Figure 6d**), had the highest

#### **Figure 6.**

*Response of* Lactuca sativa *to* Xanthobacter autotrophicus *at different levels of nitrogen and phosphate fertilizer at flowering stage 120 days after sowing. (a) Absolute control:* L. sativa *not inoculated irrigated with water; (b) relative control:* L. sativa *not inoculated fed with 100% nitrogen and phosphate fertilizer; (c)* L. sativa *with* X. autotrophicus *fed with 100% nitrogen fertilizer and 25% phosphate fertilizer; (d)* L. sativa *with* X. autotrophicus *fed with 25% nitrogen fertilizer and 100% phosphate fertilizer; (e)* L. sativa *with*  X. autotrophicus *fed with 25% nitrogen and phosphate fertilizer; (f)* L. sativa *with* X. autotrophicus *fed with 0% nitrogen and phosphate fertilizer.*

number of leaves, plant height and the highest root density, compared with *L. sativa* not inoculated fed with 100% nitrogen and phosphate fertilizer (**Figure 6b**). It is reported that *X. autotrophicus* stimulated the proliferation of root hairs in wheat, as has been observed in other plants [17, 41, 44, 137, 138] and this increased the area of exploration of the root to capture the nitrogen and phosphate fertilizer [42], as reported in other works on *X. autotrophycus* inoculation: in corn [46, 106], in wheat and in rice [43, 139].

**Figure 6** shows the effect of *X. autotrophicus* on the growth of *L. sativa* at different doses of nitrogen and phosphate fertilizer, where it was evident that *X. autotrophicus* can optimize the reduced dose of both fertilizers, in relation to nitrogen fertilizer by means of a conversion of metabolites released during photosynthesis [10, 17, 138], that reach the root to maximize the absorption of NH4NO3 while *X. autotrophicus* from inside the roots generates acid and especially alkaline phosphatases to solubilize the immobile phosphate of the soil, as well as optimize phosphate applied during the growth of *L. sativa* [140], in this trial it was demonstrated that these were the main mechanisms of *X. autotrophicus* when both fertilizers were applied in variable doses or in similar concentration, but not when in the absence of both [18, 120, 123, 124].

The possible synthesis of phytohormons by *X. autotrophicus* was supported by the test shown in **Figure 7**, in which it is evidenced by inoculation of *S. lycopersicum* with *X. autotrophicus* fed with 25% nitrogen and phosphate fertilizer (**Figure 7e**), had the highest number of leaves, fruits, plant height and the highest root density, compared to *S. lycopersicum* not inoculated fed with 100% nitrogen and phosphate fertilizer (**Figure 7b**). The positive growth of *S. lycopersicum* was due to the fact that *X. autotrophicus* had a growth promoter effect, which was detected from the beginning of wheat germination from its seed, reported to be maintained in the early stages of wheat root development [20, 41, 50], as observed in this experiment and which was similar to what was observed in root system when *X. autotrophicus* it colonizes and influences the growth of roots of beans [45, 54]. In that sense **Figure 7** shows the effect of *X. autotrophicus* on *S. lycopersicum* at different doses of nitrogen (NH4NO3) and phosphate (KH2PO4/K2HPO4) fertilizer, the growth of *S. lycopersicum* shows that the ability of *X. autotrophicus* to invade the interior of the radical system to transform compounds derived from photosynthesis into phytohormons improves the absorption and optimization of the reduced doses of NH4NO3 [13–15, 126] as well Xanthobacter autotrophicus *an Endophytic Beneficial Bacterium for Wheat and Other Plants… DOI: http://dx.doi.org/10.5772/intechopen.102066*

#### **Figure 7.**

*Response of* Solanum lycopersicum *to* Xanthobacter autotrophicus *at different levels of nitrogen and phosphate fertilizer at maturity stage 180 days after sowing. (a) Absolute control:* S. lycopersicum *not inoculated irrigated with water; (b) Relative control:* S. lycopersicum *not inoculated fed with 100% nitrogen and phosphate fertilizer; (c)* S. lycopersicum *with* X. autotrophicus *fed with 100% nitrogen fertilizer and 25% phosphate fertilizer; (d)* S. lycopersicum *with* X. autotrophicus *fed with 25% nitrogen fertilizer and 100% phosphate fertilizer; (e)* S. lycopersicum *with* X. autotrophicus *fed with 25% nitrogen and phosphate fertilizer; (f)* S. lycopersicum *with* X. autotrophicus *fed with 0% nitrogen and phosphate fertilizer.*

as of phosphorous fertilizer, and even when none of them were applied to the crop is reported that N demand was supplied by biological N2 fixation due to *X. autotrophicus* [18, 36, 52] it was also detected that it synthesized acid and alkaline phosphatase to solubilize the immobile of the soil, so that *S. lycopersicum* had a healthy growth with early formation of fruits [16, 17, 120, 135, 140] compared to *S. lycopersicum* without inoculating fed with the recommended doses both fertilizer.

**Table 2** shows the acid and alkaline phosphatase activity of *X. autotrophicus*, measured indirectly by the amount of p-nitrophenol generated when measured in the stem and roots of *S. lycopersicum* (as it is a genus and endophytic growth plant promoting species) with nitrogen and phosphorous fertilizers at 25%, of the recommended dose, there it is observed that the values of the higher and lower acid


*\*\*Values with different letter are stadistically distint according to ANOVA-Tukey (P < 0.05).*

#### **Table 2.**

*Activity of acid and alkaline phosphatases of Solanum lycopersicum at flowering stage 120 days after sowing at 25% of nitrogen and phosphate fertilizer with and without inoculating with Xanthobacter autotrophicus.*

phosphatase of the alkaline support that the healthy growth of the vegetable was due to the activity of the phosphatases synthesized by *X. autotrophicus* not only the interior of the stem and better in the root, also when this strain of *X. autotrophicus* recovered from the stem as well as from the root results suggest the importance of soil phosphorus availability in altering the interactions between leading to soil invasion by *S. lycopersicum* by *X. autotrophicus*. Overall, applying high amounts of available nutrients may reduce and increase the abundance plant-beneficial microbes and pathobiome in soil, respectively, which in return, could affect soil and plant health. This work greatly advances the mechanistic understanding why *X. autotrophicus* is a genus with high competitive capacity within the broad group of growth-promoting endophytes that synthesize acid and/or alkaline phosphatases in the absence of available phosphates and even when soluble phosphates fertilizer is applied to soil in agricultural production [141], that issue could be important for researchers working in the field of environmental microbiology, microbial ecology, plant-microbe interactions, soil health, and plant protection [16–18, 123, 142] in comparison with the activity of both phosphatases of *S. lycopersicum* without inoculation with *X. autotrophicus*, where the poor activity of both phosphatases explains that the growth of this vegetable was not as vigorous as observed in *S. lycopersicum* inoculated with *X. autotrophicus* [120, 136]. Similar results of a high acid and alkaline phosphatase activity of *X. autotrophcius* inside the roots: *Beta vulgaris, Hordeum vulgare, Pinus leiophylla, T. aestivum, Sorhgum bicolor. Z. mays*, grown in soil with insoluble phosphate problems [124, 135, 137, 143] or precipitation of the phosphate fertilizer at a lower dose than recommended (data no shown).

**Figure 8** shows that fruit of *S. lycopersicum* with *X. autotrophicus* fed with 100% nitrogen fertilizer and 25% phosphate fertilizer had the largest size and red coloration (**Figure 8**) while *S. lycopersicum* not inoculated irrigated fed with 100% nitrogen and phosphate fertilizer had a smaller size, in addition to a green coloration which means that vegetative life cycle was shorter than the fruit from not inoculate *S. lycopersicum* (**Figure 8a**). These results demonstrate the importance of *X. autotrophicus* for healthy growing plants, with a reduced dose of nitrogen and phosphorous fertilizer [54, 120, 144, 145]. **Figure 8** shows the effect of *X. autotrophicus* on the fruit of *S. lycopersicum* at a recommended dose of nitrogen fertilizer such as NH4NO3 with 25% of the phosphate fertilizer, in that sense *X. autotrophicus* is able to solubilize phosphate in soil and promote its uptake by plants are referred as phosphate solubilizing bacteria (PSB) or phosphobacteria and are included within PGPR [143]. Their counts in the rhizosphere comprise a considerable share

#### **Figure 8.**

*Fruit of* Solanum lycopersicum *with* Xanthobacter autotrophicus *at different levels of nitrogen and phosphate fertilizer at maturity stage 180 days after sowing. (a) Relative control:* S. lycopersicum *not inoculated fed with 100% nitrogen and phosphate fertilizer; (b)* S. lycopersicum *with* X. autotrophicus *fed with 100% nitrogen fertilizer and 25% phosphate fertilizer.*

Xanthobacter autotrophicus *an Endophytic Beneficial Bacterium for Wheat and Other Plants… DOI: http://dx.doi.org/10.5772/intechopen.102066*

of the rhizospheric microorganisms and vary depending on the soil location and type as well as the cultivated plants [133, 142, 146]. The results support that *X. autotrophicus* transformed organic compounds derived from photosynthesis in the inside the roots of *S. lycopersicum* in phytohormons for an efficient absorption of NH4NO3 while to optimize the phosphate fertilizer, *X. autotrophicus* by means of acid phosphatases, mainly alkaline phosphates solubilized the soil phosphates [123, 124, 142, 143, 145] and quickly absorbed the one applied consequently the fruit of the *S. lycopersicum* reached a larger size and ripened earlier in comparison with the size of the *S. lycopersicum* without inoculation fed with the recommended dose of both fertilizers [14, 16, 17, 38, 43, 50, 144].

**Figure 9** shows that *A. thaliana* with *X. autotrophicus* fed with 100% NH4NO3 (**Figure 9d**), as well as *A. thaliana* with *X. autotrophicus* fed with 50% NH4NO3, (**Figure 9h**) and *A. thaliana* with *X. autotrophicus* irrigated with only water (**Figure 9l**) had root growth inhibition, its suggested due over synthesis of phytohormons not depending of NH4NO3 concentration [20, 79, 99, 131, 147] compared to *A. thaliana* with *B. vietnamiensis* 2 fed with 100% NH4NO3 (**Figure 9c**), as well as *A. thaliana* not inoculated fed with 50% NH4NO3 (**Figure 9e**) and *A. thaliana* not inoculated irrigated with water (**Figure 9i**).

**Figure 10** shows that *A. thaliana* with *X. autotrophicus* fed with 100% NH4NO3 (**Figure 10d**), as well as *A. thaliana* with *X. autotrophicus* fed with 50% NH4NO3, (**Figure 8h**) and *A. thaliana* with *X. autotrophicus* irrigated with water (**Figure 10l**) had root growth inhibition, compared to *A. thaliana* with *B. vietnamiensis* 1 fed with 100% NH4NO3 (**Figure 10b**), as well as *A. thaliana* with *B. vietnamiensis* 1 fed with 50% NH4NO3 (**Figure 10f**) and *A. thaliana* with *B. vietnamiensis* 1 irrigated with water (**Figure 10j**). **Figures 9** and **10** show the response of the seed and stem primordia and root of *A. thalina* inoculated with *B. vietnamiensis* compared to *X. autotrophicus* at doses 100, 50 and 0% of the nitrogen fertilizer as NH4NO3 where it was evident that while a positive effect of *B. vietnamiensis* strains on *A. thaliana* was dependent on

#### **Figure 9.**

*Response of* Arabidopsis thaliana *to* Burkholderia vietnamiensis *and* Xanthobacter autotrophicus *on the germination of seed and first step of growth at seedlings stage at different dose of NH4NO3 under artificial culture media. (a)* A. thaliana *not inoculated fed with 100% NH4NO3; (b)* A. thaliana *with* B. vietnamiensis *1 fed with 100% NH4NO3; (c)* A. thaliana *with* B. vietnamiensis *2 fed with 100% NH4NO3; (d)* A. thaliana *with* X. autotrophicus *fed with 100% NH4NO3; (e)* A. thaliana *not inoculated fed with 50% NH4NO3; (f)* A. thaliana *with* B. vietnamiensis *1 fed with 50% NH4NO3; (g)* A. thaliana *with* B. vietnamiensis *2 fed with 50% NH4NO3; (h)* A. thaliana *with* X. autotrophicus *fed with 50% NH4NO3; (i)* A. thaliana *not inoculated irrigated with water; (j)* A. thaliana *with* B. vietnamiensis *1 irrigated with only water; (k)* A. thaliana *with*  B. vietnamiensis *2 irrigated with water; (l)* A. thaliana *with* X. autotrophicus *irrigated with only water.*

#### **Figure 10.**

*Effect of* Burkholderia vietnamiensis *and* Xanthobacter autotrophicus *on the germination of seed and first step of growth of* Arabidopsis thaliana *seeds directly sown in inoculated in artificial culture media at different dose of nitrogen fertilizer as NH4NO3. (a)* A. thaliana *not inoculated fed with 100% NH4NO3; (b)* A. thaliana *with* B. vietnamiensis *1 fed with 100% NH4NO3; (c)* A. thaliana *with* B. vietnamiensis *2 fed with 100% NH4NO3; (d)* A. thaliana *with* X. autotrophicus *fed with 100% NH4NO3; (e)* A. thaliana *not inoculated fed with 50% NH4NO3; (f)* A. thaliana *with* B. vietnamiensis *1 fed with 50% NH4NO3; (g)* A. thaliana *with* B. vietnamiensis *2 fed with 50% NH4NO3; (h)* A. thaliana *with* X. autotrophicus *fed with 50% NH4NO3; (i)* A. thaliana *not inoculated irrigated with water; (j)* A. thaliana *with* B. vietnamiensis *1 irrigated with water; (k)* A. thaliana *with* B. vietnamiensis *2 irrigated with water; (l)* A. thaliana *with*  X. autotrophicus *irrigated with water.*

the concentration of NH4NO3, [41, 110, 129, 148] *X. autotrophicus* inhibited seed germination and practically stem and root primordium, both effects were positive by *B. vietnamiensis* well-known plant beneficial bacteria for a domestic vegetal [149]. In opposite way *X. autotrophicus* can distinguish between a domestic plant and a weed planted in agricultural soil by stimulating the growth of the former and inhibiting the germination and growth of the latter [150]. A genetic capacity that few genera and species such as *X. autotrophicus* of growthpromoting endophytic bacteria possess and can be used to improve the growth of domestic plants and prevent the germination of weeds underline when they are dependent on the synthesis of phytohormons from compounds releasing of the seed and roots of *A. thaliana* [46, 47, 59, 79, 131, 147].
