Pantoea ananatis, a gram-negative bacterium belonging to the Erwiniaceae family, is a well-known phytopathogen isolated from many ecological niches and plant hosts. However, this bacterium also provides us with various beneficial characteristics, such as the growth promotion of their host plants and increased crop yield.
1. Introduction
Pantoea ananatis is a gram-negative, rod-shaped, aerobic, or facultatively anaerobic bacteria belonging to the class
Gammaproteobacteria and was recently reclassified into the family
Erwiniaceae from
Enterobacteriaceae [1,2][1][2].
P. ananatis was first described as
Erwinia ananas by Serrano
[3]. Some strains of
Enterobacter agglomerans,
Erwinia herbicola, and
Erwinia milletiae that form part of the
E. herbicola–
E. agglomerans complex was assigned to the genus
Pantoea [4]. Later,
Pantoea uredovora, a pathogen of
Puccinia graminis, was shown to have a high level of genomic relatedness to
P. ananas, and the two species were synonymized
[5].
P. ananas proposed by Mergaert et al.
[5] was corrected to
P. ananatis by Trüper and De’Clari
[6]. Due to this phylogenetic history,
P. ananatis contains various kinds of plant pathogenic strains
[1]. At the same time, strains that promote plant growth that are applicable to bioremediation, or have lignocellulose degradation capacity, have been found in recent years
[7].
In the field of microbial biomanufacturing,
Escherichia coli, a model organism and a member of the family
Enterobacteriaceae, which is a gram-negative facultative anaerobic rod, has been used industrially for the production of various substances because of its high growth rate and sugar consumption activity in the neutral pH range
[8,9][8][9].
Corynebacterium glutamicum, a gram-positive, rod-shaped bacterium, is capable of
L-glutamate fermentation
[10] and has been used for the industrial production of many substances by taking advantage of its characteristic cell surface
[11,12][11][12]. To date, bacterial fermentation production has been realized by mainly using
E. coli and
C. glutamicum, and many tools for genetic engineering have been developed for both strains
[9]. However, it was clear that if both strains had the trait of robustness to pH, they would be more desirable industrial substance-producing bacteria.
P. ananatis AJ13355 was isolated as an acidophilic bacterium
[13] and has been used as an excellent host organism in previous studies to produce amino acids such as
L-glutamate
[14],
L-cysteine
[15], and isoprenoids
[16,17][16][17]. The emergence of strains closely related to
E. coli and advantageous for industrial production is important in terms of increasing the potential for substance production.
2. Characteristic of Pantoea ananatis
P. ananatis has been isolated from various environments and hosts and is well-known for its phytopathogenicity.
P. ananatis causes disease symptoms in many economically important agronomic crops and forest tree species worldwide
[1]. However, several strains have been known to improve the growth of plants
[7], such as papaya
[18], red pepper
[19], sugarcane
[20[20][21],
21], poplar
[22], and rice
[23,24][23][24]. Kim et al.
[19,25][19][25] determined the genome sequence of
P. ananatis B1–9 isolated from the rhizosphere of the green onion and reported that enhanced red pepper crop yield by approximately three times and showed phosphate solubilization, sulfur oxidation, nitrogen fixation, and indole-3-acetic acid (IAA) production activities.
P. ananatis AMG521, isolated as an endophyte from rice paddies, showed the capacity to synthesize siderophores, cellulose, and IAA, and the capacity to solubilize phosphate and increase rice yield
[23].
P. ananatis strain 1.38, isolated from the rhizosphere of rice (
Oryza sativa L.), has been reported to have phosphate solubilization activity, siderophore and auxin production, and cellulose, lipase, and pectinase activities
[24]. It has long been known that
P. ananatis produces carotenoids, and it has been reported that introducing the carotenoid biosynthesis genes of
P. ananatis into a microorganism that does not produce carotenoids leads to the production of lycopene, astaxanthin, and β-carotene
[26,27][26][27]. Ten complete genomes of
P. ananatis have been determined and registered. Four were pathogenic and four had useful traits (
Table 1).
Table 1.
Complete genome of
Pantoea ananatis
.