Acinetobacter Schindleri Research Articles

Occurrence and human exposure risk of antibiotic resistance genes in tillage soils of dryland regions: A case study of northern Ningxia Plain, China

Agricultural soils are important source and sink of antibiotic resistance genes (ARGs). However, little is known about the fate of ARGs in dryland soils, while its human exposure risks were seriously overlooked. Taking the northern Ningxia Plain as a case, this study explored the occurrence of ARGs and its relationship with mobile genetic elements (MGEs), pathogens, and environmental factors. Furthermore, the concentrations of airborne ARGs by soil wind erosion and the human exposure doses of soil ARGs were evaluated. The results showed the abundances of different regions ranged from 4.0 × 105 to 1.6 × 106 copies/g. Soil ARGs are driven by MGEs, but multiply impacted by soil properties, nutrition, and bacterial community. Vibrio metschnikovii, Acinetobacter schindleri, and Serratia marcescens are potential pathogenic hosts for ARGs. Further exploration revealed the concentration of ARGs loaded in dust by soil wind erosion reached more than 105 copies/m3, which were even higher than those found in sewage treatment plants and hospitals. Skin contact is the primary route of ARGs exposure, with a maximum dose of 24071.33 copies/kg/d, which is largely attributed to ARGs loaded in dust. This study bridged the gap on ARGs in dryland soils, and provided reference for human exposure risk assessment of soil ARGs.

Identification of Bacteria Capable of Chromium Bioremediation from the Environment

With the increased urbanization and industrial development, the environment is getting polluted severely day by day. In Bangladesh, the capital city Dhaka is surrounded by a circular river system, most of which are highly polluted due to discharge of municipal and industrial untreated waste water that has been overloaded with different types of toxic heavy metals. Cr (VI) being used in various activities of industries and its improper treatment lead to contamination of the environment. This study aimed to isolate bacteria with chromium bioremediation potential from the environment. A total of 71 bacteria were isolated, of which all grew in the presence of 100 ppm, 93% in 200 ppm, 46% in 400 ppm, 6% in 600 and 4% in 1000 ppm chromium. Fourteen bacteria selected for chromium reduction by Diphenyl Carbazide Assay showed 23-89% reduction. Of these 14 isolates, 5 were tested for biosorption of chromium. Variable sorption of upto 69% was observed. The 16s rDNA of 6 candidate bacteria were sequenced. These isolates were identified as Kurthia gibsonii, Acinetobacter schindleri, Pseudomonas aeruginosa, Exigubacterium sp., Rhodococcus sp., and Bacillus sp. The reduction potential was found to be highest for Bacillus species (78%) and lowest for Kurthia gibsonii (4.8%). This study has successfully identified six potential bacterial candidates for the bioremediation of chromium (VI). Further research into the mechanisms adopted by these bacteria and genetic manipulation will help to formulate a single or mixture of isolates that can efficiently remove hexavalent chromium from polluted water. Plant Tissue Cult. & Biotech. 34(1): 71-81, 2024 (June)

Nanowire-assisted electroporation via inducing cell destruction for inhibiting formation of VBNC bacteria: Comparison with chlorination

The induction of viable but nonculturable (VBNC) bacteria with cellular integrity and low metabolic activity by chemical disinfection causes a significant underestimation of potential microbiological risks in drinking water. Herein, a physical Co3O4 nanowire-assisted electroporation (NW-EP) was developed to induce cell damage via the locally enhanced electric field over nanowire tips, potentially achieving effective inhibition of VBNC cells as compared with chemical chlorination (Cl2). NW-EP enabled over 5-log removal of culturable cell for various G+/G- bacteria under voltage of 1.0 V and hydraulic retention time of 180 s, and with ∼3–6 times lower energy consumption than Cl2. NW-EP also achieved much higher removals (∼84.6 % and 89.5 %) of viable Bacillus cereus (G+) and Acinetobacter schindleri (G-) via generating unrecoverable pores on cell wall and reversible/irreversible pores on cell membrane than Cl2 (∼28.6 % and 41.1 %) with insignificant cell damage. The residual VBNC bacteria with cell wall damage and membrane pore resealing exhibited gradual inactivation by osmotic stress, leading to ∼99.8 % cell inactivation after 24 h storage (∼59.4 % for Cl2). Characterizations of cell membrane integrity and cell morphology revealed that osmotic stress promoted cell membrane damage for the gradual inactivation of VBNC cells during storage. The excellent adaptability of NW-EP for controlling VBNC cells in DI, tap and lake waters suggested its promising application potentials for drinking water, such as design of an external device on household taps.

Identification of Acinetobacter schindleri isolated from Chinese giant salamanders (Andrias davidianus)

At a particular aquaculture facility in Zhangjiajie in China, the Chinese giant salamander (Andrias davidianus) exhibited analogous clinical manifestations, culminating in sequential mortalities. This study used rigorous aseptic sampling methods to isolate bacteria from the affected liver of salamanders to determine the causative agent behind the decline in amphibians. A bacterial pathogen was isolated from diseased A. davidianus, and the strain was named DN-3. This isolate was subjected to bacterial identification, antibiotic susceptibility assays, reinfection experiments, and biochemical profiling. The isolated bacterial strain was definitively identified as Acinetobacter schindleri using 16S rRNA sequence analysis and biochemical identification. Antibiotic susceptibility testing revealed that this isolate was susceptible to neomycin, macrolides, doxycycline, piperacillin, nitrofurantoin, and carbenicillin. Subsequent reinfection assays, in which varying concentrations of the bacterial inoculum were administered to healthy salamanders, confirmed that the pathogen elicited varying degrees of morbidity or mortality within an eight-day observation period. The median lethal dose (LD50) of A. schindleri DN-3 for A. davidianus was calculated to be 6.25×104 CFU/mL. This result supports the significant pathogenicity of the strain for A. davidianus. The findings of this study provide empirical insights into the clinical management and epidemiological control of diseases affecting A. davidianus.

Isolation and Identification of Endophytic Bacteria from Kumis Kucing Leaves (Orthosiphon aristatus Benth.)

Endophytic bacteria are in symbiosis with plants and can produce secondary metabolites similar to those produced by their host. Kumis kucing (Orthosiphon aristatus) is a traditional medicinal plant that has been proven to have many pharmacological activities, including antiviral and antibacterial. This study aims to isolate and identify endophytic bacteria from kumis kucing leaves. Endophytic bacteria were isolated from kumis kucing leaf by spreading method on Trypticase Soy Agar (TSA) media and incubated at room temperature for 24 hours. Colonies that grew with bacterial morphology were inoculated on TSA media to obtain pure cultures. Pure cultures of isolates were identified through Gram staining, 16S rRNA gene sequencing, and bacterial growth curves. There were 8 isolates with bacterial morphology which identified by Gram staining. The staining results showed that all were classified as Gram negative with rod and coccus shapes. Sequencing using the 16S rRNA gene identified 3 bacterial isolates, Acinetobacter schindleri, Pantoea agglomerans, and Pseudomonas lurida. The three bacteria have different time to reach stationary phases in order to produce their secondary metabolites.

Domestic Organic Waste: A Potential Source to Produce the Energy via a Single-Chamber Microbial Fuel Cell

Microbial fuel cell (MFC) is a method that is both effective and environmentally friendly for producing renewable electricity. Several studies have shown that one of the major challenges is the generation of electrons as a result of poor exploitation of organic substrates. One of the most talked about issues in modern molecular fusion is the reutilization of biological organic waste in an MFC. In this article, the effective utilization of domestic organic waste as an organic supply for bacterial species to generate energy was highlighted. The findings that were obtained corresponded to the one-of-a-kind MFC operation in which a voltage of 110 mV was generated in a time span of 12 days during operation with an external resistance of 500 ῼ. With an internal resistance of 117 ῼ, the maximum power density and the current density were recorded 0.1047 mW/m2 and 21.84 mA/m2, respectively. According to the results of the biological study, strains of bacteria such as Pseudomonas aeruginosa, Acinetobacter schindleri, and Pseudomonas nitroreducens are the ones responsible for producing energy. In addition, final remarks with proposals for the future have been enclosed.

Biofilm-Forming Heavy Metal Resistance Bacteria From Bungus Ocean Fisheries Port (PPS) West Sumatra as a Waters Bioremediation Agent.

<b>Background and Objective:</b> Heavy metals are one of the most worrisome pollutants due to their toxicity. Prolonged exposure to heavy metals and their accumulation and biomagnification properties adversely affect aquatic biota and human health. The ability of microorganisms to bioremediate heavy metals into non-toxic forms is one solution. The research aims of the study were to find biofilm-forming heavy metal-resistant bacteria isolated from the waters of the Bungus Samudra Fishery Port (PPS), Padang City. <b>Materials and Methods:</b> This study used a marine agar medium modified with the addition of K<sub>2</sub>Cr<sub>2</sub>O<sub>7</sub>, Pb(NO<sub>3</sub>)<sub>2</sub> and CdSO<sub>4</sub>•H<sub>2</sub>O, Marine Broth medium and Congo Red Agar medium. The research methods include, the isolation of bacteria, isolate resistance test to heavy metals, testing the ability of isolates to form biofilms and determine the ability of isolates to reduce heavy metals. Furthermore, molecular identification of bacterial isolates was carried out to determine the type of species. <b>Results:</b> Five heavy metal-resistant bacterial isolates were found that were able to form biofilms, namely isolates B3Cd, B5Cr, B7Pb, B6Pb and B3Pb. The five isolates were able to reduce heavy metal content by 38.67-61.191%. Identification of the best bacterial isolates on each heavy metal tested, namely B3Cd, B5Cr and B7Pb, respectively, showed the type of <i>Acinetobacter schindleri</i>, <i>Acinetobacter</i> sp. and <i>Bacillus</i> sp. <b>Conclusion:</b> These three selected potential isolates can be used as bioremediation agents in metal-polluted waters in the future.

Proline Content, Physiological and Agronomic Characters of Rice (Oryza sativa cv. Inpari Unsoed 79 Agritan) under Treated with PGPR in Saline Medium

Tidal areas near the coastline are prone to salinity impacts as a negative impact of seawater intrusion which causes dissolved salt levels to increase. The biological approach using PGPR is an environmentally friendly approach. The aim of the study was to examine the effectiveness of useful bacteria from saline soils to increase the resistance of rice plants to salinity stress. The research was carried out from April to October 2022 in the Lab. Agronomy & Horticulture Faperta UNSOED. This research was experimental research using liquid culture techniques for cultivating plants using AB Mix media. The design used was a randomized block design with three replications. The treatments were included Control (P0), Acinetobacter junii (P1), Bacillus tropicus (P2), Acinetobacter schindleri (P3), Pseudomonas stutzeri (P4), Bacillus altitudinis (P5), Bacillus cereus (P6), dan Bacillus subtilis (P7). The results of the study showed that Diazotrophic Bacteria inoculation can increase the resistance of rice plants to rice plants by increasing proline production, increasing net assimilation rates and relative growth rates. Acinetobacter schindleri, Bacillus subtilis and Bacillus tropicus are potential N2 fixing bacterial strains to increase the growth and yield of rice under saline conditions. Treatment of Acinetobacter schindleri was able to provide the highest grain yields reaching 16.95 g/plant.

Genome Resource for Acinetobacter schindleri H4-3-C1: An Endophyte of Pseudostellaria heterophylla with Degradation Activity to Toxins Produced by Fungal Pathogens

Acinetobacter schindleri is an endophyte of Pseudostellaria heterophylla, a traditional Chinese herbal plant. It has high degradation activity to toxins produced by fungal pathogen Fusarium graminearum. Here, we deployed PacBio single-molecule real-time long-read sequencing technology to generate a complete genome assembly for the Acinetobacter schindleri H4-3-C1 strain and obtained 1.59 Gb of clean reads. These reads were assembled to a single circular DNA chromosome with a length of 3,265,024 bp, and no plasmid was found in the genome. Totals of 3,193 coding sequences, 91 transfer RNA, 21 ribosomal RNA, and 75 small RNAs were identified in the genome. This high-quality genome assembly and gene annotation resource will facilitate the excavation of the zearalenone degradation gene and provide valuable resources for preventing and controlling toxigenic fungal diseases of P. heterophylla. [Formula: see text] Copyright © 2022 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Isolation and molecular identification of halotolerant diazotrophic bacteria from The Northern Coastal of Pemalang, Central Java, Indonesia

Abstract. Purwanto, Oktaviani E, Leana NWA. 2022. Isolation and molecular identification of halotolerant diazotrophic bacteria from The Northern Coastal of Pemalang, Central Java, Indonesia. Biodiversitas 23: 5814-5821. Plant Growth Promoting Bacteria can fix nitrogen, a very important macronutrient for plant growth. However, the application of urea as a source of this macronutrient has a negative impact on the environment. Therefore, developing biofertilizers using N-fixing bacteria is an environmentally friendly technology. Therefore, this research aimed to isolate and analyze the diversity of N2-fixing bacteria from saline rice fields. The soil samples were taken from the rhizosphere of rice plants in Nyamplung Sari Village, Petarukan District, Pemalang Regency. Meanwhile, 9 (nine) isolates of nitrogen-fixing bacteria have been isolated, which can fix N2. The isolates can bind to N2, but only a few can produce IAA. The nitrogen-fixing ability of diazotrophic bacteria ranged from 17.85 ppm to 29.05 ppm. Isolate Jn3 has the highest ability to fix nitrogen, reaching 29.05 ppm, while Jn3, J, J12, J5, Kn1, and A3 can produce IAA with values of 2.00, 2.69, 2.22, 1.76, 3.47, and 1.79 ppm, respectively. Based on the 16S rRNA analysis and phylogeny construction, the isolated bacteria were identified in 3 (three) clusters. The first cluster was identified as Pseudomonas stutzeri and Acinetobacter junii (Kn1 and Jn3), while the second was identified as Bacillus cereus, Bacillus tropicus, Bacillus altitudinis, and Bacillus subtilis (Jn, Jn1, A3, and K3 isolates). The third cluster was identified as Bacillus pumilus, Acinetobacter baumanii, and Acinetobacter schindleri (J12, J5, and J). In addition, our study reported the findings of Acinetobacter baumannii and Acinetobacter schindleri species that can fix nitrogen.

Markedly decreased growth rate and biofilm formation ability of Acinetobacter schindleri after a long-duration (64 days) spaceflight.

The objective of this study was to investigate the effects of long-duration space flight on the biological characteristics of Acinetobacter schindleri (A. schindleri). In this study, an A. schindleri strain was collected from condensate water of the Shenzhou-10 spacecraft and then was sent into space again to the Tiangong-2 space lab for a long-duration spaceflight (64 days). Later, the impacts of the long-duration spaceflight on phenotype, genome and transcriptome of A. schindleri were analyzed. It was found that the long-duration spaceflight markedly decreased the growth rate and biofilm formation ability of A. schindleri. Furthermore, comparative genomic and transcriptomic analyses revealed that the decreased growth rate might be associated with differentially expressed genes (DEGs) involved in transmembrane transport, energy production and conversion, and biofilm was reduced due to downregulation of the pil and algR genes. The findings are of major importance for predicting bacterial pathogenesis mechanisms and possible spacecraft contamination during long-duration spaceflights in the future.

Heterogeneity of the Tissue-specific Mucosal Microbiome of Normal Grass Carp (Ctenopharyngodon idella).

Microbiome plays key roles in the digestion, metabolism, and immunity of the grass carp (Ctenopharyngodon idella). Here, we characterized the normal microbiome of the intestinal contents (IC), skin mucus (SM), oral mucosa (OM), and gill mucosa (GM) of the grass carp, as well as the microbiome of the sidewall (SW) of the raising pool, using full-length 16S rRNA sequencing based on the PacBio platform in this specie for the first time. Twenty phyla, 38 classes, 130 families, 219 genera, and 291 species were classified. One hundred four common classified species might be core microbiota of grass carp. Proteobacteria, Bacteroides, and Cyanobacteria were the dominant phyla in the niche of grass carp. Proteobacteria and Bacteroides dominated the taxonomic composition in the SM, GM, and OM, while Proteobacteria, Planctomycetota, and Cyanobacteria preponderated in the IC and SW groups. Microbiota of IC exhibited higher alpha diversity indices. The microbial communities clustered either in SW or the niche from grass carp, significantly tighter in the SW, based on Bray-Curtis distances (P < 0.05). SM, GM, and OM were similar in microbial composition but were significantly different from IC and SW, while IC had similarity with SW due to their common Cyanobacteria (P < 0.05). Differences were also reflected by niche-specific and differentially abundant microorganisms such as Noviherbaspirillum in the SM and Rhodopseudomonas palustris, Mycobacterium fortuitum, and Acinetobacter schindleri in GM. Significantly raised gene expression was found in IC and SM associated with cell cycle control, cell division, chromosome, coenzyme transport and metabolism, replication, recombination and repair, cell motility, post-translational modification, signal transduction mechanisms, intracellular trafficking, secretion, and vesicles by PICRUSt. This work may be of great value for understanding of fish-microbial co-workshops, especially in different niche of grass carp.

Biodegradation α-endosulfan and α-cypermethrin by Acinetobacter schindleri B7 isolated from the microflora of grasshopper (Poecilimon tauricola).

Extensive use of pesticides has led to the contamination of ecosystem. Therefore, it is important to isolate potential new pesticide-degrading bacteria. For the biodegradation of α-endosulfan and α-cypermethrin, a new bacterium was isolated from the body microflora of grasshopper (Poecilimon tauricola). Based on biochemical, morphological, and 16S rRNA sequence analysis, the isolated strain B7 was identified as Acinetobacter schindleri. This bacterial strain was screened for its α-cypermethrin and α-endosulfan degrading potential with minimal salt medium (MSM) and non-sulfur medium (NSM), respectively. When glucose was added to non-sulfur medium containing α-endosulfan (100mg/L) and minimal salt medium containing α-cypermethrin (100mg/L), both pesticide degradation and bacterial growth were increased. Acinetobacter schindleri B7 was able to degrade 67.31% of α-endosulfan and 68.4% of α-cypermethrin within 10days. The degradation products of pesticides were determined by HPLC. As a result, A. schindleri, a Gram-negative bacterium, can inevitably be used in the biological treatment of environments exposed to pesticides.

The role of gut microbiota in clinical complications, disease severity, and treatment response in severe alcoholic hepatitis.

Dysbiotic gut bacteria engage in the development and progression of severe alcoholic hepatitis (SAH). We aimed to characterize bacterial communities associated with clinical events (CE), identify significant bacteria linked to CE, and define bacterial relationships associated with specific CE and outcomes at baseline and after treatment in SAH. We performed 16-s rRNA sequencing on stool samples (n=38) collected at admission and the last follow-up within 90 days in SAH patients (n=26; 12 corticosteroids; 14 granulocyte colony-stimulating factor, [G-CSF]). Validated pipelines were used to plot bacterial communities, profile functional metabolism, and identify significant taxa and functional metabolites. Conet/NetworkX® was utilized to identify significant non-random patterns of bacterial co-presence and mutual exclusion for clinical events. All the patients were males with median discriminant function (DF) 64, Child-Turcotte-Pugh (CTP) 12, and model for end-stage liver disease (MELD) score 25.5. At admission, 27%, 42%, and 58% had acute kidney injury (AKI), hepatic encephalopathy (HE), and infections respectively; 38.5% died at end of follow-up. Specific bacterial families were associated with HE, sepsis, disease severity, and death. Lachnobacterium and Catenibacterium were associated with HE, and Pediococcus with death after steroid treatment. Change from Enterococcus (promotes AH) to Barnesiella (inhibits E. faecium) was significant after G-CSF. Phenylpropanoid-biosynthesis (innate-immunity) and glycerophospholipid-metabolism (cellular-integrity) pathways in those without infections and the death, respectively, were upregulated. Mutual interactions between Enterococcus cecorum, Acinetobacter schindleri, and Mitsuokella correlated with admission AKI. Specific gut microbiota, their interactions, and metabolites are associated with complications of SAH and treatment outcomes. Microbiota-based precision medicine as adjuvant treatment may be a new therapeutic area.

Actinobacillus pleuropneumoniae Surviving on Environmental Multi-Species Biofilms in Swine Farms.

Actinobacillus pleuropneumoniae is the etiologic agent of porcine contagious pleuropneumonia, an important respiratory disease for the pig industry. A. pleuropneumoniae has traditionally been considered an obligate pig pathogen. However, its presence in the environment is starting to be known. Here, we report the A. pleuropneumoniae surviving in biofilms in samples of drinking water of swine farms from Mexico. Fourteen farms were studied. Twenty drinking water samples were positive to A. pleuropneumoniae distributed on three different farms. The bacteria in the drinking water samples showed the ability to form biofilms in vitro. Likewise, A. pleuropneumoniae biofilm formation in situ was observed on farm drinkers, where the biofilm formation was in the presence of other bacteria such as Escherichia coli, Stenotrophomonas maltophilia, and Acinetobacter schindleri. Our data suggest that A. pleuropneumoniae can inhabit aquatic environments using multi-species biofilms as a strategy to survive outside of their host.

The lower respiratory tract microbiome of critically ill patients with COVID-19

COVID-19 infection may predispose to secondary bacterial infection which is associated with poor clinical outcome especially among critically ill patients. We aimed to characterize the lower respiratory tract bacterial microbiome of COVID-19 critically ill patients in comparison to COVID-19-negative patients. We performed a 16S rRNA profiling on bronchoalveolar lavage (BAL) samples collected between April and May 2020 from 24 COVID-19 critically ill subjects and 24 patients with non-COVID-19 pneumonia. Lung microbiome of critically ill patients with COVID-19 was characterized by a different bacterial diversity (PERMANOVA on weighted and unweighted UniFrac Pr(> F) = 0.001) compared to COVID-19-negative patients with pneumonia. Pseudomonas alcaligenes, Clostridium hiranonis, Acinetobacter schindleri, Sphingobacterium spp., Acinetobacter spp. and Enterobacteriaceae, characterized lung microbiome of COVID-19 critically ill patients (LDA score > 2), while COVID-19-negative patients showed a higher abundance of lung commensal bacteria (Haemophilus influenzae, Veillonella dispar, Granulicatella spp., Porphyromonas spp., and Streptococcus spp.). The incidence rate (IR) of infections during COVID-19 pandemic showed a significant increase of carbapenem-resistant Acinetobacter baumannii (CR-Ab) infection. In conclusion, SARS-CoV-2 infection and antibiotic pressure may predispose critically ill patients to bacterial superinfection due to opportunistic multidrug resistant pathogens.

Molecular systematic and phylogenetic analysis of indigenous bacterial isolates with potential as bioremediation agent based on 16S rRNA gene analysis

Liquid biomedical waste is a form of medical waste from community health centers (Pusat Kesehatan Masyarakat or Puskesmas) with high levels of health hazardous organic contaminants. Bioremediation is an alternative way to eliminate toxic components in liquid waste. A bacteria community that can be used as component of organic waste bioremediation is indigenous hydrolytic and non-pathogenic to low-pathogenic bacteria. From previous studies, 4 hydrolytic indigenous bacterial isolates with such characteristics were obtained from liquid clinical wastes of two health centers in Semarang City, namely H1, H3, H5 (from Puskesmas Halmahera), and T3 (from Puskesmas Tlogosari Kulon). This study aimed to reveal the molecular identity and kinship these bacterial isolates to understand more of their properties as consortium of bioremediation agent. Molecular identification and phylogenetic tree construction works were carried out based on 16S rRNA gene sequences. Sequences of 16S rRNA gene sequences were obtained by isolation and gene amplification using the PCR method followed by sequencing. Based on the results of molecular identification, the four isolates studied were in the same class, namely Gammaproteobacter with Phylum Proteobacter. H1 bacterial isolates have 98.01% similarity with Acinetobacter schindleri. H3 and H5 isolates share the same genus, Stenotrophomonas, with 99.79% similarity with S. maltophiphila and 97.69% with S. acidaminiphila, respectively. T3 isolate had a similarity of 98.85% with Pararheinheimera aquatica species, which was widely known as a potent bioremediation agent. The phylogenetic tree design with the MEGA 6 program showed that the H3 and H5 isolates had the closest kinship compared to the other two isolates, while the T3 isolates had the farthest relationship with the 3 other isolates. This is in line with the fact that T3 isolate was originated from a different location separating it from 3 other isolates.

Furfural biotransformation in Acinetobacter baylyi ADP1 and Acinetobacter schindleri ACE.

To determine furfural biotransformation capabilities of Acinetobacter baylyi ADP1 and Acinetobacter schindleri ACE. Acinetobacter baylyi ADP1 and A. schindleri ACE could not use furfural as sole carbon source but when acetate was used as substrate, ADP1 and ACE biotransformed 1g furfural/l in 5 and 9h, respectively. In both cases, the product of this biotransformation was difurfuryl-ether as shown by FT-IR and 1H and 13C NMR spectroscopy. The presence of furfural decreased the specific growth rate in acetate by 27% in ADP1 and 53% in ACE. For both strains, the MIC of furfural was 1.25g/l. Nonetheless, ADP1 biotransformed 2g furfural/l at a rate of 1g/l/h in the stationary phase of growth. A transcriptional analysis of possible dehydrogenases involved in this biotransformation, identified that the areB and frmA genes were highly overexpressed after the exposure of ADP1 to furfural. The products of these genes are a benzyl-alcohol dehydrogenase and an alcohol dehydrogenase. Acinetobacter baylyi ADP1 is a candidate for the biological detoxification of furfural, a fermentation inhibitor present in lignocellulosic hydrolysates, with the possible direct involvement of the AreB and FrmA enzymes in the process.

Pseudomonas spp. and other psychrotrophic microorganisms in inspected and non-inspected Brazilian Minas Frescal cheese: proteolytic, lipolytic and AprX production potential

ABSTRACT: The most consumed cheese in Brazil, Minas Frescal cheese (MFC) is highly susceptible to microbial contamination and clandestine production and commercialization can pose a risk to consumer health. The storage of this fresh product under refrigeration, although more appropriate, may favor the growth of spoilage psychrotrophic bacteria. The objective of this study was to quantify and compare Pseudomonas spp. and other psychrotrophic bacteria in inspected and non-inspected MFC samples, evaluate their lipolytic and proteolytic activities and their metalloprotease production potentials. Twenty MFC samples were evaluated: 10 inspected and 10 non-inspected. Counts of psychrotrophic bacteria and Pseudomonas spp., evaluation of the proteolytic and lipolytic potential of the isolates, and identification of potential producers of alkaline metalloprotease (AprX) were assessed. The mean total psychrotrophic counts were 1.07 (±2.18) × 109CFU/g in the inspected samples and 4.5 (±5.86) × 108CFU/g in the non-inspected, with no significant difference (p=0.37). The average score of Pseudomonas spp. was 6.86 (±18.6) × 105 and 2.08 (±3.65) × 106 CFU/g for the inspected and non-inspected MFC samples, respectively, with no significant difference (p=0.1). Pseudomonas spp. represented 0.06% and 0.004% of psychrotrophic bacteria found in inspected and non-inspected MFC samples, respectively. Collectively, 694 psychrotrophic strains and 47Pseudomonas spp. were isolated, of which 59.9% and 68.1% were simultaneously proteolytic and lipolytic, respectively. Of the 470 psychrotrophs isolated from inspected and 224 from non-inspected cheese samples, 5.74% and 2.23% contained aprX, respectively, while 100 and 86.96% of the Pseudomonas spp. isolates in inspected and non-inspected cheese samples contained the gene. The production potential of AprX did not, however, determine the proteolytic activity on plates of these isolates under the conditions evaluated in this study. Of total, 65.63% of the psychrotrophs that contained aprX gene were confirmed as Pseudomonas spp., using genus-specific PCR. Phylogenetic analysis of the 16S rRNA gene of the other psychrotrophs that were potential producers of AprX identified them as Serratia spp. (n=7), Raoultella ornithinolytica (n=1), and Acinetobacter schindleri (n=1) in the inspected samples and Psychrobacter sanguinis (n=1) and Leuconostoc mesenteroides (n=1) in the non-inspected samples. The production conditions of Brazilian MFC of these samples, while meeting the legal determinations, are not sufficient to control Pseudomonas and other spoilage-related psychrotrophs. Thus, stricter hygienic measures are required during the formal production of this type of cheese.

Physiological and transcriptional comparison of acetate catabolism between Acinetobacter schindleri ACE and Escherichia coli JM101.

Acinetobacter bacteria preferentially use gluconeogenic substrates instead of hexoses or pentoses. Accordingly, Acinetobacter schindleri ACE reaches a high growth rate on acetate but is unable to grow on glucose, xylose or arabinose. In this work, we compared the physiology of A. schindleri ACE and Escherichia coli JM101 growing on acetate as the carbon source. In contrast to JM101, ACE grew on acetate threefold faster, had a twofold higher biomass yield, and a 45% higher specific acetate consumption rate. Transcriptional analysis revealed that genes like ackA, pta, aceA, glcB, fumA, tktA and talA were overexpressed while acsA, sfcA, ppc and rpiA were underexpressed in ACE relative to JM101. This transcriptional profile together with carbon flux balance analysis indicated that ACE forms acetyl-CoA preferentially by the AckA-Pta (acetate kinase-phosphotransacetylase) pathway instead of Acs (acetyl-CoA synthetase) and that the glyoxylate shunt and tricarboxylic acid cycle are more active in ACE than in JM101. Moreover, in ACE, ribose 5-phosphate and erythrose 4-phosphate are formed from trioses, and NADPH is mainly produced by isocitrate dehydrogenase. This knowledge will contribute to an understanding of the carbon metabolism of Acinetobacter species of medical, biotechnological and microbiological relevance.