Genomic analysis and plant growth-promoting potential of a Serratia marcescens isolated from food

A genomic analysis of the potential application of a Serratia marcescens strain in the plant-growth promotion. We performed whole-genome sequencing of Serratia marcescens isolated from a Minas Frescal Cheese. The genomic repertoire revealed a bacterium of agricultural and biotechnological interest. In the plant-growth promotion traits, we highlight genes encoding proteins possibly responsible for the biosynthesis of phytohormone indole acetic acid, organic compounds that act in iron uptake, and the Phosphate solubilization system. Genes encoding for enzymes like the versatile L-asparaginase stimulates the development of seeds and grains and can benefit the food industry due to a mitigation effect on acrylamide and notably, has medical applications as a chemotherapeutic agent or is applicable by its antimicrobial and anti-inflammatory properties. Moreover, functional diversity of genes encoding for resistance to different metals and metabolism of xenobiotics genes can be found in this strain, reinforcing its biotechnological potential. The versatile enzymes that can be produced by S. marcescens benefit the food, pharmaceutical, textile, agronomic, and cosmetic industries. The relevant genetic systems of S. marcescens described here may be used to promote plant growth and health and improve the environment. To the best of our knowledge, this is the first genome sequence report on S. marcescens isolated from cheese, with potential application as promoting plant growth and providing a baseline for future genomic studies on the development of this species.


Introduction
Serratia marcescens, classified under the family Yersiniaceae of the order Enterobacterales (Adeolu et al., 2016), is capable of thriving in a broad range of environments.
The wide variety of gene repertoire enables S. marcescens to be a ubiquitous microorganism, successful in diverse environments and with multipurpose applications or effects. For example, marine S. marcescens demonstrated antioxidant and antibacterial activity against some Gram-positive and Gram-negative bacteria (Gangadharan et al., 2020). Moreover, oil spills in aquatic ecosystems can be bioremediated by a biodispersant produced by S. marcescens characterized by low toxicity, high biodegradability, and good ecological acceptability (dos Santos et al., 2021).
In the terrestrial environment, the species can act as a pathogen to animals (Friman et al., 2019;Ishii et al., 2012).
However is agronomically relevant with its antifungal effect (Troskie et al., 2014). Furthermore, it can be considered a biocontrol agent with herbicidal activity (Kamran et al., 2017) and as a plant growth-promoting rhizobacteria (PGPR), improving the health and development of their host plant by acting on the solubilization of inorganic P present in the soil (Rodrıǵuez & Fraga, 1999).
Alternative approaches can improve the soil and global water healthy, once continuously contaminated by the human being, to maintain the exorbitant life cycle. Due use of bacteria systems in biotechnology plus the promise of S. marcescens role in several mechanisms, it could be used in different scenarios, including azo dyes degradation to soil decontamination (Mahmood et al., 2017).
Functional diversity of genes encoding for enzymes have evidenced an important assignment for S. marcescens in the biotechnological industry, including segments such as food, cosmetics, chemical, and pharmaceutical (dos Santos et al., 2021;Falade & Ekundayo, 2021).
Both disease and therapy are present in the dual role of S. marcescens in the clinic, responsible for outbreaks (Cristina et al., 2019) was even identified as an opportunist in outbreaks during covid-19 treatment (Amarsy et al., 2020). However, it has shown an extensive presence of enzymes with antimicrobial and anti-inflammatory properties proving effective to even resistant microorganisms and with the possibility of use as a chemotherapeutic agent in different cancer cell lines (Abdel-Razik et al., 2019;Pavithrra & Rajasekaran, 2020).
The broad niche and functional diversity of the S. marcescens are probably influenced by and, at the same time, influence on the highly dynamic genome (Cristina et al., 2019), turning relevant the periodical investigation of the genetic background of emerging S. marcescens strains from various sources. Moreover, the potential application of the strain to promote plant growth was explored from the genotypic perspective.

Isolation and characterization of the Serratia marcescens
The Serratia marcescens strain was isolated from a Gram-negative pool of bacteria from a previous analysis of Minas Frescal Cheese according to the methodology of Silva et al., 2020. Subsequently, the strain was isolated in Mueller Hinton Agar. Genomic DNA of the bacterial strain was extracted with a NucleoSpin Tissue kit (Macherey-Nagel & Germany, 2018) in conformity with the manufacturer's protocol.

Characterization of the Serratia marcescens
The bacterial strain was identified to be Serratia marcescens and was deposited at the Genbank under the number SUB9616311, BioProject and Biosample accession number are PRJNA729465 and SAMN19116778, respectively. The genome has Total Length (bp) 4,969,854 and GC Content 59.6%; 4,722 CD; 4 rRNA; 81 tRNA; 2 CRISPR.

Genomic repertoire
The diversified genomic repertoire of S. marcescens made it possible to group them into different sets of genes according to the benefits presented. Table 1 presents genes related to several systems involved in plant-growth promotion. Research, Society andDevelopment, v. 11, n. 1, e29611124799, 2022 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v11i1.24799 Source: Data from the research using the bioinformatics tools already described in the methodology.
The genes encoded in the set described in table 1 are related to several physiological processes in plants and contribute directly or indirectly to their growth and development, including mechanisms as the solubilization of minerals and siderophores that act in iron uptake.
The sequence analysis indicated that in the present Serratia marcescens genome was observed interesting genes for industries (Table 2). Source: Data from the research using the bioinformatics tools already described in the methodology.
The wide variety of gene repertoire allows S. marcescens to arouse the interest of different branches of the industry, especially food, chemical, and pharmaceuticals. In the latter, the emphasis would be on agents with antimicrobial capacity that are increasingly important in this sector.
Some sets of genes can indirectly support plant growth promotion.  Source: Data from the research using the bioinformatics tools already described in the methodology.
Healthy environmental conditions are essential for plant survival and growth. For example, the set of genes in Table 3 supports the degradation of substances discarded by industries, such as synthetic textile dyes and heavy metals, helping to support the soil quality.
Growth-promoting bacteria that have the ability to survive in places with the presence of antibiotics and heavy metals have greater added value. Table 4 presents some relevant genes in this context. Source: Data from the research using the bioinformatics tools already described in the methodology.
Bacterial resistance to metals and antimicrobials present in S. marcescens can bring advantages and allow the plant to survive in environments with multiple stresses, making the bacteria attractive, even for use in bioremediation of the environment.
Complementary characteristics in PGPR bacteria, such as the ability to defend against plant parasites, which can play an important role, are described in table 5. Source: Data from the research using the bioinformatics tools already described in the methodology.
The presence of compounds of microbial origin with insecticidal and larvicide potential is interesting for plant growth promoter candidates because it also allows its use in biocontrol activity.

Genes involved in the plant growth promotion traits
In the present Serratia marcescens genome was observed genes related to several systems involved in plant-growth promotion (table 1). Among the systems found, the Tryptophan biosynthesis pathway, a system related to several physiological processes in plants, including the biosynthesis of phytohormone indole acetic acid (IAA) (Khan et al., 2017), another system also observed in the present sample. Unfortunately, IAA biosynthesis does not have its mechanism fully elucidated. However, it is known that phytohormones such as auxins and cytokinins are involved in critical physiological processes of plants such as cell wall elongation and cell division stimulus, respectively (Xie et al., 2020). The IAA can act as an inducer compound of Induced Systemic Resistance (ISR). The ISR is an important plant defense mechanism against a broad range of pathogens, parasitic weeds, and even insect herbivores. PGPR producing IAA may enhance the resistance against pathogens. The ISR has already been shown to be effective in rhizobacterium S. marcescens acting as a PGPR (Ryu et al., 2013).
The present genome also contains genes that express the non-protein amino acid gamma-aminobutyric acid (GABA), a well-known neurotransmitter in the mammalian body first isolated in 1949, but with less than 20 years of study in plant organisms. Until no less than six years ago, the influence of GABA in the plant-growth was described (Ramesh et al., 2017) identify a plant 'GABA receptor' that inhibits anion passage through the aluminum-activated malate transporter family of proteins (ALMT) and propose that GABA regulation of ALMT activity could function as a signal that modulates plant growth, development, and stress response.
This study also demonstrates other growth promoters in plants that act indirectly, such as the biosynthesis and transport capacity of several polyamines, more precisely putrescine, cadaverine, and spermine, which stimulate the endogenous production of growth promoters such as IAAs and reducing growth inhibitors (A. A. Amin et al., 2011). Chitin degradation is also an indirect growth mechanism present in this Serratia strain, proving to be an important factor in several microbiological agents in controlling pathogenic fungi in several plant species (Das et al., 2010). The capacity of acetoin synthesis complements promoting indirect growth as a precursor agent of volatile bacterial compounds (Sharifi & Ryu, 2018).
It also has a mechanism for the production of siderophores, organic compounds that act in iron uptake. Since iron is abundant in its insoluble form in the soil, siderophores act on the excretion of substances, forming soluble compounds with iron and then being absorbed (Parmar & Chakraborty, 2016). The siderophores that the present strain produces are Bacterioferritin, enterobactin, and isochorismate.
Another system for promoting plant growth found in this genome involving the solubilization of minerals is the Phosphate solubilization system, both organic and inorganic. Phosphate is commonly found in the soil in its insoluble form (Rodrıǵuez & Fraga, 1999), so the performance of these mechanisms becomes essential for the absorption of the mineral. It is worth noting that the present strain also contains the gcd and pqq gene complex, which respectively code for glucose dehydrogenase and pyrroloquinoline quinone, also called the quinoprotein glucose dehydrogenase complex. A complex that acts in the release of gluconic acid in the soil, helping in the solubilization of inorganic phosphate. Highlighting that the pqq gene acts as a cofactor for the performance of glucose dehydrogenase (Abreo & Altier, 2019). Although phosphate is rarely present in its organic form in the soil, with average measurements around 1 ppm or even less in some cases, its role is also crucial in promoting plant growth. To be absorbed, soil bacteria act by hydrolyzing organic phosphate to inorganic phosphate and then proceed to absorption with the originally inorganic phosphate (Rodrıǵuez & Fraga, 1999).
Still, on mineral solubilization, the present S. marcescens genome has zinc solubilization genes, which in turn have a direct relationship with gross growth. Bearing in mind that zinc deficiency can cause plant growth retardation, chlorosis, reduced leaf size, greater susceptibility to heat and fungal infections, it can affect grain and pollen yield, water uptake, and, in some plant species, the yellowing of the leaves (Kamran et al., 2017). Moreover, the solubilization of zinc also ends up helping in the production of siderophores.
Other genes presented by this strain promote chemotaxis activity. This activity is important because it is known that PGPR tends to have positive chemotaxis towards higher concentrations of sugars, thus being able to bring more substrates to plants and directly influence growth (Pedraza et al., 2010).

Genes involved in antimicrobial activities or important enzymes for industry
The functional diversity of the S. marcescens genome presents genes of interest for the pharmaceutical and medical sector, likewise the food, cosmetics, and fuel industries (Table 2).
Among some products, we can highlight the versatile enzyme L-asparaginase that includes the medical application of its antimicrobial and anti-inflammatory properties besides its use as a chemotherapeutic agent in different cancer cell lines (Abdel-Razik et al., 2019). The strategy of using novel therapeutic agents isolated from S. marcescens has been previously demonstrated in a marine strain with antioxidant and antibacterial activity against some Gram-positive and Gram-negative bacteria. (Gangadharan et al., 2020).
The food sector benefits from L-asparaginase mitigation effect due to toxic acrylamide, making it an essential component in food processing industries. This sector can demand the enzyme either considering its application in plant growth promotion. The L-Asparagine is the most abundant metabolite for the storage and transport of nitrogen in plants and impacts vegetable production. The L-asparaginase breaks down asparagine into aspartic acid and ammonia, providing nutrition directly and indirectly as a precursor of other amino acids that stimulate plant growth. Furthermore, the L-asparaginase is essential for developing seeds and grains (Damare & Kajawadekar, 2020).
The antimicrobial property is also of particular interest in Gramicidin D, a natural antimicrobial peptide produced by the soil microorganism Bacillus brevis ATCC 8185 during its sporulation phase. This ionophoric antibiotic forms membrane channels resulting in pores' formation, leading to cell disruption and loss of solutes and ions. The Gramicidin D has been effective against antibiotic resistant microorganisms, inhibiting the genetic material synthesis and respiration and reducing ATP, leading to cell death (Pavithrra & Rajasekaran, 2020).
The high hemolytic activity of Gramicidin D turns it more suitable where there is low hemolytic activity, as in antimalarial activity against Plasmodium falciparum (Gumila et al., 1997) and plants with some benefits already been demonstrated in oat roots (Hodges et al., 1971).
The food sector can also benefit from the presence of the peptide tyrocidine that has an unexplored antifungal effect against some agronomically relevant fungal phytopathogens (Troskie et al., 2014). The tyrocidines can be associated with gramicidin, either encoded by our S. marcescens strain in an antimicrobial compound called tyrothricin that shows activity against bacteria, fungi, and some viruses. This antibiotic demonstrated a low risk of resistance development in vitro, turning it a valuable therapeutic option to consider against the antibiotic resistance process (Stauss-Grabo et al., 2014).
Additionally, even new strategies proposed to treat antibiotic resistance, like bacterial predation, effective against some Gram-negative bacteria (Rames, 2020), find a barrier in our strain as a result of the metalloprotease serralysin that can reduce the ability of some predators to attach to the S. marcescens, conferring protection (Garcia et al., 2018). Serralysin, a virulence factor used medicinally as a proteolytic enzyme, is therapeutically useful in the management of pain and inflammation as a broad spectrum anti-inflammatory drug (Tiwari, 2017), digests non-living tissue, blood clots, cysts, and arterial plaque (Rouhani et al., 2020) and has an anticancer potential (Araghi et al., 2019).
Our S. marcescens sample revealed the peroxiredoxins OsmC/Ohr, Prx5, and Prx6 proteins. Peroxiredoxins are ubiquitous peroxidases that play an important role in antioxidant defense and regulating cell signaling pathways (Perkins et al., 2015). Ohr is involved in the host-pathogen interface, while OsmC participates more in the oxidative defense (Alegria et al., 2017). Moreover, Prx5 and Prx6 are being related to cancer prevention, although more studies are necessary to understand the interaction pattern with cancer cells (Forshaw et al., 2019).
For the best of our knowledge, all the four proteins associated with peroxiredoxins discussed above (OsmC/Ohr, Prx5, and Prx6) were not reported in Serratia marcescens before, revealing its potential and possible use in the host-pathogen interface and cancer management.
The use of substances produced by the Serratia genus and present in our lineage has benefits, including agronomy. Plant protecting properties of the biosurfactant serrawettin, for example, turns the S. marcescens an interesting candidate for controlling and preventing Oomycete pathogens infestation of plants (Strobel et al., 2002). Mechanisms of plant growth promotion include the synthesis of siderophores which can solubilize and sequester iron from the soil. The presence of the siderophore pyoverdine may provide iron to plants. This supply helps the bacteria to protect plants against the inhibitory effects of high concentrations of nickel, lead, and zinc (Burd et al., 2000).
The S. marcescens genome also carries genes encoding enzymes like Laccase, a component of prokaryotic lignindegrading systems. This ligninolytic genetic repertoire is reinforced by the gene YefX encoding dye-decolorizing peroxidase (DyP). This heme peroxidase is more efficient in degrading lignin than classical peroxidase considering the ability of DyP to degrade aromatic compounds that constitute approximately 90% of the lignin (Melo-Nascimento et al., 2020). Thus, the industry can benefit from lignin uses. Additions of alkali lignin to pet and human food can be an important fiber source, especially considering that high nutritional fiber relates to low occurrences of colon câncer (Naseem et al., 2016).
The DyP ability to degrade lignin can benefit its utilization as a carbon source. Considering that lignin is one of the most abundant organic macromolecules in the biosphere, it can constitute a renewable carbon feedstock, potentially reducing the use of petroleum-derived chemicals (Brown & Chang, 2014).
The dye-decolourizing activity that gives name to the peroxidase may also benefit the industry operating in bioremediation, degrading synthetic dyes, and remediating phenolic environmental pollutants. Particularly important considering that synthetic dyes are employed in diverse industries such as food, textile, plastics, food, and pharmaceutical (Falade and Ekundayo, 2021). Bioremediation strategies using S. marcescens have been developed as a promising alternative for marine ecosystems impacted by petroderivatives (dos Santos et al., 2021).
The versatility is also present in Lipases, ubiquitous enzymes that hydrolyze ester bonds of triglycerides at oil-water. Its enantioselectivity in biocatalytic hydrolysis is being used in the pharmaceutical industry to produce key intermediates of the diltiazem hydrochloride used in circulatory disorders pharmacos and the anti-inflammatory ketoprofen (Long et al., 2007;Shibatani et al., 2000). Another application of the enzyme is its use to produce monoacylglycerols and diacylglycerols, which have the advantage of being biodegradable and non-toxic and are widely used as emulsifiers in food, pharmaceutical, and cosmetic industries (Zied et al., 2018). In addition, the lipases are known for their ability in the industry of oil and lipid processing, detergent production, and biotransformation (García-Silvera et al., 2018;Zied et al., 2018). Some studies have shown some applicability for S. marcescens lipase, such as petroleum biodegradation regenerating contaminated areas, generation of emulsifiers from cheap vegetable oils, and biodiesel production (García-Silvera et al., 2018;Peixoto et al., 2017;Zied et al., 2018).
Some microorganisms have been using the Butanol biosynthesis system for biofuel production. Butanol is a sustainable technology for alternate and renewable energy, being less corrosive and with higher energy content per unit mass than traditional fuels. The butanol potential includes its use as a solvent and a platform chemical in the cosmetic and pharmaceutical industry (Lv et al., 2021).

Degradation of azo dyes and hydroxybenzoate degradation
There is a need for healthy environmental conditions, such as water purity and soil integrity and strength, to promote plant growth. The global aquatic resources undergo endless threats due to the discharge of several substances such as synthetic textile dyes and heavy metals, mainly from industries (Mahmood et al., 2017).
The azo dyes are a group of synthetic chemicals present in wastewaters dumped by textile industries. The water contaminated by this group of dyes affects the nearby waters used for agriculture and other purposes. Moreover, it is hard to remove from agricultural soils because of their complex structure (Mahmood et al., 2017).
Following these lines, the contaminated water irrigates plants that incorporate these chemical substances bringing harmful effects both for the plant and for the consumer (Mahmood et al., 2017).
Our group found in the S. marcescens genome the system of degradation azo dyes (Table 3). It is of common knowledge that this system is responsible for decolorized azo dyes through NADH-ubiquinone: oxidoreductase enzyme activity. This group of dyes is associated with impaired plant metabolism, health, and growth (Mahmood et al., 2017).
The S. marcescens use may provide the soil and plant azo dyes decontamination, which can be associated with plant growth and metabolism improvement. Besides, healthy soil is essential to promote a whole agriculture quality (Ahmed et al., 2016).
Plants naturally contain relevant levels of phenolic compounds that are essential to many metabolism events, such as growth, reproduction, and protection against pathogens . In these lines, the S. marcescens genome showed a hydroxybenzoate degradation gene set, which must be considered.

Degradation of nitro compounds, degradation of arylsufatase and N-heterocyclic aromatic compound degradation
Other harmful substances are released in the environment, such as 2,4,6-Trinitrotoluene (TNT), released from demilitarization facilities. This compound is highly toxic and hazardous to all organisms, plants, and hu mans included. The nitroreductase protein family is involved in reducing nitrogen-containing compounds, such as TNT (You et al., 2015). Some bacteria strains are already used in plants as a detoxifying tool for this kind of environment. Here we report the presence of the nitroreductase protein family in the S. marcescens genome, which can also be used for the plant environment decontamination and improvement.
It is common knowledge that arylsulfatase is important to SO4 2plant uptake throughout the mineralization of organic sulfur (S) to SO4 2and it is from bacteria strains (Knauff, Schulz, & Scherer, 2003). Sulfur plays a fundamental role in plant metabolic processes and protein production, which prompts the plant growth or development and filling of grains, for example (Hawkesford, 2007). The S absence is harmful to the plant, and the arylsulfatase is essential to provide this nutrient for the plant (Knauff et al., 2003).
Besides, heterocyclic compounds are a group of chemicals also found in the environment. Some of these compounds can accumulate in the soil, leading to toxicity to plants and humans (Seo, Keum, & Li, 2009). The S. marcescens genome sequencing showed the arylsulfatase system and N-heterocyclic aromatic compound degradation system presence, which indicates one more important role of this bacterium in promoting plant growth and health.

Quinate degradation
Quinate is an important compound produced and used by plants. It is a precursor for chlorogenic acids (CGAs) biosynthesis. The CGAs act in leaves and fruits as a protective agent against pathogens and fungus and play an antioxidant role, protecting the plant against UV radiation damage (Gritsunov et al., 2018).
The quinate degradation system is essential to provide the active compound from the quinate pathway and could be used to help in plant protection promotion, which could allow their growth and metabolism improvement.

Metabolism of xenobiotics by cytochrome P450 and hydroxybenzoate degradation and degradation of various xenobiotics compounds
The cytochrome P450 (CYP) is an enzymatic protein superfamily found in several organisms, such as mammals, fungi, plants, and bacteria. It is composed of enzymes essential in many plant metabolic pathways, plant growth, development, and defense (Xu et al.,, 2015). The CYP family is also important in the detoxication of herbicides in plants (Stiborová et al., 2000).
Although the cytochrome P450 is already found in plants, exogenous origin use could be an essential tool for improving plant metabolism. Our group described, throughout the genome S. marcescens sequencing, the presence of this xenobiotics metabolism system. When applied in plant improvement, this strain could be used to deliver this system to the plant, and it can be applied in several contexts. For example, the use of contaminated soil for agriculture or plant cultures that demand high herbicide doses require a robust detox mechanism, which could not be sufficient (Gong et al., 2005). In these scenarios, the use of exogenous systems of xenobiotics metabolism could allow this kind of culture and even improve plant growth and health.
Besides, many systems of degradation of xenobiotics compounds were found in S. marcescens sequencing. These pathways are essential in restraining oxidative damage, xenobiotics detox, and many stress responses that are important in plant metabolism and growth (Gong et al., 2005). These systems are composed of several proteins, such as glutathione Stransferases (GSTs). Gong and colleagues (2005) showed that in vivo, the GSTs expression was related to changes in plant growth and shoot regeneration in vitro. These data demonstrate de GSTs influence in plant growth and metabolism, which could be applied in biotechnological approaches through S. marcescens usage.

Phenylacetate degradation
The Phenylacetic acid (PAA), also known as phenylacetate, belongs to a group called auxins, a class of hormones essential in plant metabolism (Cook, 2019).
PAA was described as a growth-promoting hormone, and later studies, comparing PAA with the auxin IAA, demonstrated PAA's higher activity in stimulating lateral root. The few studies with this auxin suggest PAA's predominant role in root growth and plant regular growth maintenance (Cook, 2019). Possibly PAA is important in other plant mechanisms, but more studies must deep investigate its whole function.
The S.marcescens sequencing showed a phenylacetate degradation system which must be considered in its biotechnology use, once this strain characteristic could promote the antagonist effect proposed.

Genes responsible for the resistance to different metals and antibiotics
The success of bioremediation is related to the bacteria's ability to survive in a contaminated environment, among others, by antimicrobials and heavy metals (Table 4). It is the case of our strain. For example, the Cpx Regulatory System Upregulates the Multidrug Resistance Cascade. The Cpx Stress Response has a global effect in a diversity of signal transduction pathways, including the bacterial resistance to antimicrobials (Guest & Raivio, 2016).
The excessive presence of heavy metals in the environment leads to several problems in soil, such as impaired fertility, decreased microbial activity, and yield losses. This problem affects plant growth and metabolism and carries toxicity to human health (Kacálková et al., 2009). The S.marcescens sequencing showed some relevant genes in heavy metals transporting and zinc/cadmium/mercury/lead-transporting ATPase. These systems are important to transport these heavy metals and could be used in a biotechnology approach to a detox tool for plants that grow in the contaminated soil.
Besides these systems, the copper resistance system was also found in S. marcescens sequencing. The excessive copper accumulation in plants leads to several deleterious effects, such as reduced seed germination, impaired plant growth, low yield, and formation of ROS (reactive oxygen species) (H. Amin et al., 2021). Therefore, the presence of an exogenous system could control copper plant concentration and promote plant growth and health.
Metal resistance has been described in a co-selection mechanism with antibiotic resistance, particularly relevant under environmental conditions of metal stress. The selective pressure to survive under stress conditions might contribute to plant growth-promoting bacteria evolve mechanisms to tolerate the uptake of heavy metal and/or the antibiotic presence in soil, for example (Yang et al., 2021).
PGPR bacteria presenting antibiotic and metal resistance genes in parallel have been identified in environments with multiple stress in which the survivor bacterium is probably benefited by acquiring resistance to both causes of stress (Wani & Irene, 2013).
This co-selection may occur as a co-resistance when genes encoding resistance to heavy metals and antimicrobial agents are physically linked to each other (Bazzi et al., 2020). This association has already been described in S. marcescens with tetracycline resistance and also to chloramphenicol and kanamycin in this case, which is genetically linked to As, Cu, Hg, and Ag resistance genes (Gilmour et al., 2004).
Other ways occur with the Cross-resistance when the same resistance mechanism confers resistance to both heavy metals and antimicrobial agents. Frequently related to multi-drug efflux pumps and the least common mechanism of coselection, the Co-regulatory resistance occurs when resistant genes to antimicrobial agents and heavy metals are controlled by a mutual regulatory protein (Bazzi et al., 2020). These mechanisms of co-selection support the direct correlation between antibiotic resistance genes with the concentration of antibiotics and metals found in the manure of Chinese swine farms (Yang et al., 2021).

Genes responsible for the nematicidal and larvicidal kill genes
Compounds of microbial origin have been showing a positive protection effect combating plant-parasites (table 5). For example, in the root-knot nematode that impacts the global agricultural production, acetaldehyde demonstrated nematicidal activity by direct contact killing besides the fumigation inhibiting egg hatching (Huang et al., 2020).
The nematicidal effect of other substances as serrawettin and chitinase potentially produced by our strain has already been found in Serratia sp. genetically related to S. marcescens. The presence of these compounds, according to the author, is important to turn this strain into an attractive candidate as a sustainable alternative for biocontrol in crops of agricultural interest (Méndez-Santiago et al., 2021).
The broad niche and functional diversity of the S. marcescens are probably influenced by the highly dynamic genome (Cristina et al., 2019), turning relevant a periodical investigation of the genetic background from various sources, concerning its possible pathogenicity. This research collaborates in this context with the genetic repertoire of a Serratia marcescens isolated from food. In addition, the potential application of this strain as a plant growth promoter was evaluated from a genotypic perspective.

Conclusion
The S. marcescens systems described here are relevant in the plant biotechnology approach representing an alternative in promoting plant growth and health. All these systems could improve different mechanisms, both in the plants and their environment. In addition, understanding the genetic background governing this strain may bring new insights into the ecology of Serratia marcescens.
To the best of our knowledge, this is the first genome sequence report on S. marcescens isolated from cheese, with potential application as promoting plant growth and providing a baseline for future genomic studies. Future investigations of others Serratia marcescens isolated from food will allow comparative analysis that may help to establish a model of the genetic background of the association between S. marcescens with plants and the food production process.