Microbiological Studies Research Articles

The relationship between microbial population ATP and quantitative PCR bioburdens in diesel fuel microcosms.

Historically, fuel microbiology studies have relied on culture data. Potentially relevant but unculturable bacteria were not detected. Although ATP can quantify total microbial bioburdens in fuels, it cannot differentiate among the taxa present. Quantitative PCR (qPCR) testing promises to fill this gap by quantifying targeted amplicon sequences thereby detecting both culturable and non-culturable taxa and quantifying specifically targeted taxa. In this study, fluid samples drawn from the fuel, interface and water phases of fuel over water microcosms were tested for cellular ATP concentration ([cATP]) and qPCR bioburdens. Additionally, surface swab samples from steel corrosion coupon surfaces exposed to each of these three phases were collected and tested for total ATP concentration ([tATP]) and qPCR bioburdens. Statistical relationships between ATP and qPCR bioburdens were examined. Correlation coefficients between the two variables were matrix dependent and ranged from negligible (|r|=0.2) to strong (|r|=0.7). When results were categorized into negligible, moderate and heavy bioburdens, parameter agreement was again matrix dependent. Percentage agreement between [ATP] and qPCR gene copies ranged from 11 % to 89 % - with qPCR-bioburden ratings typically being greater than ATP-bioburden ratings.

Biogeochemical features of the formation of Holocene sediments in Lake Dukhovoe (Eastern Baikalia)

A 6-meter core of Holocene sediments from Lake Dukhovoe was studied. As shown by the radiocarbon dating of lacustrine sediments, Lake Dukhovoe was formed in the Early Holocene (10 cal ka BP). The upper 180 cm of sediment is represented by sapropel, and the boundary of lake sediments is at 293 cm. This is an early stage of lake evolution, devoid of biogenic sedimentation. The microbiological studies of the sediment were carried out, which showed a high total number of heterotrophic bacteria in the upper (0–15 cm) and deeper (110–180 cm) sapropel intervals. Mineral bottom sediments (180–293 cm) are characterized by the presence of groups of phosphorus-reducing and ferromanganese bacteria. The contents of Na, Mg, Al, Si, Al, Ca, Fe, Mn, Zr and Cr in sapropel are within the average concentrations for the earth’s crust, and U and Mo exceed them.

Physicochemical and Microbiological Studies of Various Brands of Vanilla Ice Cream Manufactured in Bangladesh

Physicochemical and Microbiological Studies of Various Brands of Vanilla Ice Cream Manufactured in Bangladesh

Exogenous endophthalmitis caused by Citrobacter Koseri

Aims/Purpose: To present a case of exogenous endophthalmitis caused by Citrobacter Koseri.Methods: We present a 66‐year‐old man that works in an animal laboratory exercising their care, who came to the emergency department due to sudden loss of vision in his left eye. Using indirect ophthalmoscopy, we observed a dense hemovitreous that prevented visualization of the posterior structures. An ocular ultrasound was performed in which suggestive signs of retinal detachment are intuited, so we decided to perform an exploratory vitrectomy. During exploratory vitrectomy via pars plana, a dense fibrinoid vitreous was observed, with a tear at XIIh of more than 1 h in diameter. The vitrectomy was completed successfully after suturing the sclerotomies.Results: The postoperative period evolved adequately, but 3 days later, the patient presented to the emergency room with pain and severe ocular inflammation. On physical examination, he presented intense conjunctival hyperemia, signs of corneal melting, and increased ocular tone. Endophthalmitis was diagnosed and treatment was started with reinforced intravitreal and eye drops antibiotics and anti‐inflammatories. 24 h later, the patient went back with an extrusion of the lens that was sent to microbiological study. On physical examination, we observed corneal melting that produced complete corneal perforation with extrusion of purulent and vitreous material and an urgent evisceration was performed. Two days later, the microbiological samples confirmed the Citrobacter Koseri microorganism.Conclusions: Cases of exogenous endophthalmitis caused by Citrobacter are limited in the literature. In this case, exposed suture material and the epidemiological history of the patient were suspected as the source of infection. Despite early diagnosis and intensive treatment, the clinical course of Citrobacter endophthalmitis is very aggressive and has a poor visual prognosis. In our case it ended with evisceration.

Current state, microbiological monitoring, and prevention of water pollution in Lake Baikal

Since 2003, Limnological Institute SB RAS has been holding the International Baikal Microbiological Symposia “Microorganisms and Viruses in Aquatic Ecosystems” every four years, and even in the “covid” year 2020, it was held “in remote mode.” The proper functioning of viral and bacterial communities is the basis for the stable quality of aquatic ecosystems. New ecological problems for the Lake Baikal ecosystem are becoming more and more acute, and the scientific research, the results of which are presented and discussed at these symposia for different aquatic ecosystems around the world, should help to find solutions for preserving the water quality now and in the future. We analyze the long-term microbiological studies of the water quality in the littoral and pelagic zones of Lake Baikal carried out by numerous authors, and propose a specific scheme of microbiological monitoring of this unique aquatic ecosystem required by the environmental regulatory authorities. Specific measures to prevent pollution of oligotrophic lake waters are also provided; these measures can be rapidly implemented now.

Quality examination of ice cream products made from melon grown in Khorezm area

The results of qualitative examination of melon ice cream, its raw materials, preparation technology, vitamin C content in various recipes of ice cream, as well as regulatory documents on various microbiological safety standards in the product, methods for studying the necessary microbiological indicators, as well as microbiological studies of melon ice cream in storage in different conditions are presented.

Efficiency of photodynamic inactivation Actinomyces israelii and Prevotella melaninogenica.

The goal of our work was to develop acomposition for antimicrobial photodynamic inactivation (aPDI) of anaerobic periodontopathogenic pathogens. The three test groups were as follows: light plus doxycycline (L+DOX+), light plus doxycycline and hypericin (L + DOX + HYP +), and control groups. aPDI was evaluated by the number of grown colonies on adense nutrient medium after 12, 24, and 48 hours of bacterial suspension cultivation. Based on the results of microbiological studies, the combined photosensitising effect of asubinhibitory dose of doxycycline and hypericin was determined. The delay of growth of A. israelii, P. melaninogenica in the second group (L+DOX+HYP) was significantly significant compared to the first group (L+DOX+), and the statistical difference in colony formation activity was found for both gram-positive and gram-negative cultures (p<0.05). aPDT is apromising therapeutic alternative for the local treatment of purulent-inflammatory diseases of various localisation caused by antibiotic-resistant bacteria, including in the oral cavity (Fig. 3, Ref.57). Text in PDF www.elis.sk Keywords: peri-implant diseases, photodynamic therapy, photosensitiser, anaerobic bacteria.

Microbiome Profiling Demonstrates Concordance of Endotracheal Tube Aspirates With Direct Lower Airway Sampling in Intubated Patients

BackgroundEndotracheal aspirates (ETAs) are widely used for microbiological studies of the respiratory tract in intubated patients but involve sampling through an established endotracheal tube using suction catheters, both of which can acquire biofilms that may confound results. Research questionDoes standard clinical ETA in intubated patients accurately reflect the authentic lower airway bacterial microbiome? Study design and methodsWe applied comprehensive quantitative bacterial profiling using 16S rRNA V1V2 gene sequencing to compare bacterial populations captured by standard clinical ETA with contemporaneous “gold standard” samples acquired directly from the lower airways through a freshly-placed sterile tracheostomy tube in 13 patients undergoing percutaneous tracheostomy following prolonged (median 15 days) intubation. Metrics of bacterial composition, diversity and relative quantification were applied to samples. ResultsPre-tracheostomy ETAs closely resembled the gold-standard immediate post-tracheostomy airway microbiomes in bacterial composition and community features of diversity and quantification. Endotracheal tube and suction catheter biofilms also resembled cognate ETA and fresh tracheostomy communities. Interpretation.Unbiased molecular profiling demonstrates that standard clinical endotracheal aspirate sampling has good concordance with the authentic lower airway microbiome in intubated patients.

Development of a method for collecting bronchoalveolar lavage from calves for microbiological diagnosis of bronchopneumonia

A serious problem for the health of cattle, especially in highly productive animals, is infectious bronchopneumonia, which occurs when exposed to numerous adverse environmental factors and opportunistic microorganisms. Infectious bronchopneumonia is an important problem in the livestock industry and remains a major cause of significant economic losses in dairy herds and feedlots due to high morbidity and mortality rates, in addition to negatively affecting growth, reproductive performance and life expectancy. Therefore, the development of a new method for intravital minimally invasive diagnosis of calves with acute catarrhal bronchopneumonia using bronchoalveolar lavage sampling for subsequent microbiological studies is relevant. The invention relates to veterinary medicine and can be used in intravital diagnostics of bronchopneumonia in calves by isolating microorganisms that initiate the purulent-inflammatory process from samples of bronchoalveolar contents taken in the area of the tracheal bifurcation. A method for intravital diagnosis of bronchopneumonia in calves includes transnasal introduction to a sick animal of a sterile silicone medical tube with a diameter of 4 mm (the internal diameter of the hole is 3 mm), a wall thickness of 1.0 mm and a length of 150 cm, until slight resistance and a repeated cough reflex appear, upon reaching in the area of the tracheal bifurcation, the nasogastric tube is moved back 1 cm, a disposable syringe with a volume of 50 ml is attached to the free end, and with its help, 30-40 ml of sterile isotonic saline solution (0.9% NaCl solution, 37° C) is injected into the trachea, and then immediately aspirate up to 10 ml of bronchoalveolar contents.

Analysis of the quantitative composition of the dental biofilm depending on the state of the hard dental tissues

The microflora of the oral cavity affects not only the development and course of the pathology of the hard dental tissues but also the effectiveness of its treatment and prevention. Therefore, it is equally important for a dentist to determine the species composition of microorganisms and their quantitative characteristics. The aim of the work was to study the quantitative composition of the planktonic form of the dental biofilm of the vestibular surface of the cervical teeth in young patients; its analysis in patients with a wedge-shaped defect, cervical caries and clinically intact teeth. A microbiological study of the dental biofilm of intact premolars of 33 caries-resistant patients (average age [23.90±5.34] years) was conducted. All patients were divided into three groups depending on the condition of the hard dental tissues. The dental biofilm removed from the lesion was additionally examined in patients with wedge-shaped defects. Microorganisms were identified by morphological, tinctorial and biochemical characteristics. A quantitative study of the population level was carried out by counting colony-forming units (CFU) in one gram of biomaterial which was expressed as a decimal logarithm (lg CFU/g). An imbalance between representatives of pathological and normal microflora was determined. Patients with cervical caries had a significantly higher chance of having Str. mutans and Lactobacterium in the dental biofilm, and a lower chance Str. γ-haemolyticus (p&lt;0.05). It confirms the role of Str. mutans and Lactobacterium in the etiology of cervical dental caries. There were no significant differences between the quantitative composition of the dental biofilm of patients of different groups that is probably related to the study of its planktonic component, the criteria for forming groups and the high level of caries resistance of the examined enamel. The obtained results can be useful in prescribing treatment and preventive measures for patients with cervical pathology of the teeth as well as in evaluating their effectiveness. In our opinion, it will contribute to a significant reduction in its prevalence and intensity among young people. Keywords: microorganisms, оral cavity, wedge-shaped defect, cervical caries.

Mucormycosis: Cytomorphological Spectrum in Fine-Needle Aspiration Cytology.

Mucormycosis is a fungal infection that can affect multiple organs. The role of fine-needle aspiration cytology (FNAC) in its diagnosis is not well documented. The objective of this study was to describe the detailed cytomorphologic features of mucormycosis on FNAC samples. A retrospective analysis of all cases diagnosed as mucormycosis on FNAC between January 2014 and July 2021 was performed for detailed cytomorphological evaluation and correlation to clinical data and microbiological studies wherever available. FNA was computed tomography-guided (n = 38), ultrasonography-guided (n = 31) or palpation-guided (n = 12), and slides were reviewed in two cases. A total of 83 cases of mucormycosis were evaluated. An immunocompromised setting was observed in 48 cases. The most common site of FNA was the lung (n = 57) followed by liver, soft tissue, palate, mediastinum, orbital/ocular region, and lymph node. Isolated renal involvement, a unique feature, was seen in seven cases. The aspirates were necrotic to pus-like or blood-mixed particulate. Broad, nonseptate, foldable, ribbon-like fungal hyphae showing right-angled branching were seen. The tissue reaction was predominantly necro-inflammatory (n = 36), bland necrotic (n = 22), mixed inflammatory (n = 16), suppurative (n = 5), necrotizing granulomatous (n = 3), and granulomatous (n = 1). Immunocompromised patients showed mixed inflammatory responses more frequently. Fungal culture was positive for Rhizopus species in 2/13 cases and molecular testing in two additional cases corresponding to Rhizopus and Syncephalastrum spp. FNA provides quick and conclusive diagnosis of mucormycosis from varied anatomic sites enabling prompt institution of therapy. The tissue response is variable and to some extent dependent on the immune status of the patient.

Microbiological characteristics and antibiotic sensitivity of &lt;i&gt;Mycobacterium avium&lt;/i&gt; subsp. &lt;i&gt;paratuberculosis (MAP)&lt;/i&gt; isolated on the territory of Western Siberia

The results of the studies of microbiological features of cultures of standardized and clinical strains isolated from biological material of the animals on the territory of Western Siberia belonging to Mycobacterium avium subsp. paratuberculosis (MAP) are presented. Microbiological studies of the pathogens consisted of the bacterioscopic method (staining of smears of cultures according to Ziehl – Neelsen) and the culture method (processing of biomaterial by the method of A.P. Alikaeva with subsequent sowing of the obtained sediment on Lowenstein-Jensen and Finn-2 egg nutrient media with mycobactin). In addition, biochemical tests with the cultures isolated from the material were used, including examination of colony growth at 30, 37 and 42 C, on the medium with sodium salicylate, with 5% sodium chloride, nitrate reduction, determination of amidase, catalase, arylsulfatase activity, hydrolysis of Tween-80 and a biological method consisting of intravenous infection with suspensions of standardized and clinical strains of non-linear white mice. The results of the studies showed that the cultures of clinical strains belonged to the 3rd group of mycobacteria according to the Runyon classification and their properties were identical to the standardized strain of M. paratuberculosis, which allows us to attribute them to mycobacteria of paratuberculosis. Antibiotic sensitivity studies of the standardized strain of M. paratuberculosis (Central-Lubinsky) and clinical strains revealed their susceptibility to all the drugs used in the studies. In a biological assay, mice infected with paratuberculosis pathogens had lower body weight than in the control groups. Autopsy revealed enlargement of lungs, spleen and liver, single purulent foci on liver, spleen and mesentery, and the liver was marbled, the mucosa of the small intestine is not changed. The growth intensity of cultures from the biomaterial (lungs, liver, spleen) was 2(++) to 3(+++) to 4(++++) points, the growth intensity of the cultures from the mucosa of the small intestine is 0(+/-) points. Bacterioscopic examination of smears of colony cultures of the studied pathogens isolated from the internal organs of mice of the experimental groups and stained by Ziehl – Neelsen staining showed the presence of single acid-fast granular bacilli arranged in groups or in the form of a "palisade", which is characteristic of the causative agent of paratuberculosis. The biological method of research on laboratory animals revealed the susceptibility of nonlinear white mice to the tested cultures and the possibility of reproducing experimental paratuberculosis infection on them.

Оценка качества воды и донных отложений Северо-Крымского канала перед запуском основного потока воды по содержанию углеводородов и некоторым микробиологическим показателям (весна 2022 г., полуостров Крым)

In the Spring 2014, the supply of Dnieper water to the North Crimean Canal (NCC) was stopped. The canal was previously used for centralized water supply and agriculture in the steppe part of Crimea. After 8 years, the active use of the Dnieper water in the Crimea requires comprehensive studies of its quality. Traditionally, microbiological studies are used to assess the ecological condition of water areas. In addition, it is important to monitor components of hydrocarbon origin such as aliphatic hydrocarbons. In general, the NCC waters by microbiological parameters (the number of heterotrophic, lipolytic and hydrocarbon-oxidizing bacteria) and the concentration of hydrocarbons can be attributed to the oligosapropic, low-polluted zone. According to the level of aliphatic hydrocarbons, the bottom sediments of the studied section of the NCC and the soil in the area adjacent to the canal are classified as naturally pure.

EFFECTS OF THE LONG-TIME RIPENING OF BEEF UPON ITS QUALITY PARAMETERS

Subject. The subject is beef obtained from young bulls of the Aberdeen-Angus beef breed. Purpose. The purpose is to investigate the effects of dry ripening of beef upon its quality and safety parameters. Methods. The content of protein (by mass) was determined by the content of total nitrogen according to Kjeldahl followed by distillation of ammonia; the content of water (by mass) – by drying the portion to constant weight at the temperature of 105ºС; content of fat (by mass) – Soxhlet method; pH – potentiometric method; water-binding ability – by pressing the test sample; sensorial parameters – consumer assessment using a hedonic scale of 9 levels; rheological parameters – using a universal electromechanical testing machine; microbiological parameters – based on the total number of microorganisms in 1 g of product. Results. The quality parameters of long-ripened meat (within 21 days) were studied in comparison with traditionally ripened meat (within 5 days). Sensorial assessment has shown the benefits of long-ripened meat. It was found that in long-ripened beef samples the content (by mass) of protein and fat is higher by 12.97% and 21.41%, respectively; water-binding capacity is 10.69% higher. This leads to a reduction in meat moisture loss during heat treatment by 6%. It has been determined that the penetration force of long-ripened meat is less important compared to similar parameters of traditionally ripened meat. Microbiological studies have shown that meat on the 21st day of ripening corresponds to standard values. Scope of results. A technological instruction for the production of fermented meat has been developed. The developed solution was tested in industrial conditions, and a production inspection certificate was obtained.

Recovery of Stressed Escherichia coli Culturability using Selective Media with Penicillin Binding Proteins for Bioburden Testing

This study aimed to assess the effectiveness of selective media enriched with Penicillin-binding proteins (PBPs) in bioburden testing and the recovery of stressed Escherichia coli. Five distinct E. coli strains were subjected to experimentation utilizing two antibiotics to induce stress, simulating real-world scenarios where bacteria face various stressors, including antibiotics. The deliberate stress induction aimed to observe how stressed bacteria respond and recover in the presence of PBPs, vital cell wall components targeted by antibiotics. Multiple antibiotics ensured a comprehensive evaluation of stress responses. PBP1 tended to have a milder inhibitory effect on bacterial growth compared to both PBP2 and PBP3 across various growth media and strains. PBP2 demonstrated variable effects, displaying a nuanced impact depending on the growth medium and strain. In contrast, PBP3 consistently exerted a stronger inhibitory effect on bacterial growth. The strain of E. coli exhibited a significant influence on growth characteristics, reflecting strain-dependent responses to experimental conditions. Growth media and specific PBPs also displayed notable effects on colony forming units (CFUs) and percentage recovery (PR). Modified media generally supported higher CFUs and PR compared to standard media, showcasing the importance of media composition. Buffer choice also significantly impacted CFUs and PR, underlining the need for careful buffer standardization. Overall, the type of PBP used significantly affected E. coli colony numbers, as indicated by a highly significant p-value (p≈2.04×10-16). This study’s insights into the impact of selective media, PBPs, and bacterial strains on stressed E. coli recovery contribute to optimizing recovery protocols in microbiological studies. Comparisons between penicillin and cefixime treatments revealed higher CFU values in modified media, indicating their efficacy. Different PBPs showcased variations in CFU and PR, emphasizing their role in stressed E. coli recovery. The study sheds light on the multifaceted interactions between antibiotics, PBPs, media, and bacterial strains, vital for understanding antibiotic responses. These findings provide critical insights into designing effective recovery strategies and advancing microbiological studies.

SELECTION OF HISTOPLASMA FARCIMINOSUM STRAIN TO CREATE A REMEDY FOR EQUINE LYMPHANGOITIS

Epizootic lymphangitis is a chronic infectious disease, the causative agent of which is the fungus Histoplasma farciminosum and continues to cause significant outbreaks worldwide, despite several decades of epidemiological surveillance, diagnosis and prevention. Therefore, research on the selection of strains in the composition of anti-lymphangoitic agents is very relevant. The following strains of Histoplasma farciminosum fungus were used for selection: 410, T, YH, 5th, 4th, 5th, 17th, 21st, 8ZH. Microbiological studies of the studied strains were carried out with the study of cultural and morphological properties, the isolation of saccharolytic, proteolytic enzymes, the formation of catalase, oxidase, etc. To determine the biological properties of strains, agar and Saburo broth were used. In the course of the work, the cultural and biochemical properties of 9 strains of fungi were studied: 410, T, YH, 5th, 4th, 5th, 17th, 21st, 8ZH, as well as their growth on the Saburo nutrient medium. The validity of choosing a strain to create an anti-lymphangoitic agent of horses should include the following parameters: the strain, regardless of the type and genus, should have homogeneous cultural and morphological properties without signs of dissociation and abundant bacterial mass yield, In total, the selected strains will be a biological reserve that can be used in the development of diagnostic tools and prevention of equine lymphangoitis

Hematological and Biochemical Parameters of Macropod Progressive Periodontal Disease in Wild Western Gray Kangaroos

Macropod progressive periodontal disease (MPPD), known as Lumpy Jaw, poses a persistent and potentially fatal threat in Western gray kangaroos when they are kept in captivity. Such a condition leads to the development of osteomyelitis and sepsis in Western gray kangaroos (Macropus fuliginosus). This case study presented the inaugural examination of hematological and biochemical aspects of MPPD with a progression toward sepsis in a captive environment. The primary objective of this research was to pinpoint hematological and biochemical indicators associated with severe MPPD in a Western gray kangaroo held in captivity. The study employed various methods, including clinical, radiographical, hematological, and biochemical analyses, as well as microbiological study methods. The case was a 2.5-year-old male wild Western gray kangaroo with fever (39.7 °C), dehydration, dyspnea, tachycardia, and involuntary jaw clenching due to stress and agitation. The kangaroo had a history of lethargy, anorexia, swelling of the soft tissues of the lower jaw on the left side, and tenderness during palpation. A radiograph of the head revealed mandible proliferative lesions. The hematological and biochemical examinations indicated an increase in the total count of leucocytes, level of neutrophils, number of erythrocytes, hematocrit level, and lymphopenia. Increased activity of alkaline phosphatase, amylase, and creatinine elevated azotemia. There was a decrease in the content of albumin, glucose, and total bilirubin. The bacteria, consisting of Fusobacteriaceae spp., Porphyromonadaceae spp., and Bacteroidaceae spp., were found and identified in all samples. However, this comprehensive diagnosis of MPPD based on clinical signs, radiography, and especially hematological and biochemical parameters of the septic process can be helpful in diagnosis and treatment.

Development of bread technology with the use of grain raw materials

Bread made with sourdough is the leader among other baked goods in nutritionist ratings. It is a wonderful source of energy and has a low glycemic index. Making bread using sourdough meets environmental requirements. The use of grain mixtures and their individual components helps to increase the nutritional value of bread and the quality of bread. This paper presents the possibilities of developing bread of nutritional value using sprouted components. The article presents the results of the study. Quality and nutritional value of bread with grain mixtures and components. Organoleptic, physical and chemical, microbiological and rheological studies of semi-finished products and bread of high nutritional value using grain components were carried out. It is proven that the introduction of 28 % of sourdough starter with components from grains, whish were prepared and sprouted in advance, to the mass of flour has a positive effect on the nutritional value of bread.

Freshwater Sponges as a Neglected Reservoir of Bacterial Biodiversity.

Freshwater sponges (Spongillida: Demospongiae), including more than 240 described species, are globally distributed in continental waters (except for Antarctica), where they cover both natural and artificial surfaces. However, fragmentary studies have targeted their microbiome, making it difficult to test hypotheses about sponge-microbe specificity and metabolic relationships, along with the environmental factors playing key roles in structuring the associated microbial communities. To date, particular attention has been paid to sponges (family Lubomirskiidae) that are endemic to Lake Baikal. Few other freshwater sponge species (e.g., Ephydatia spp., Eunapius spp., and Spongilla lacustris), from lakes and rivers spanning from Europe to South and North America, have been targeted for microbiological studies. Representatives of the phyla Proteobacteria, Bacteroidetes, and Actinobacteria largely predominated, and high differences were reported between the microbiome of freshwater and marine sponges. Several bacterial strains isolated from freshwater sponges can produce bioactive compounds, mainly showing antibiotic activities, with potential application in biotechnology. Understanding the roles played by sponge microbiomes in freshwater ecosystems is still in its infancy and has yet to be clarified to disentangle the ecological and evolutionary significance of these largely under-investigated microbial communities. This review was aimed at providing the main available information on the composition and biotechnological potential of prokaryotic communities associated with healthy freshwater sponges, as a neglected component of the global sponge microbiome, to stimulate researchers interested in the field.

Multifaceted photoreceptor compositions in dual phototrophic systems – A genomic analysis

For microbes and their hosts, sensing of external cues is essential for their survival. For example, in the case of plant associated microbes, the light absorbing pigment composition of the plant as well as the ambient light conditions determine the well-being of the microbe. In addition to light sensing, some microbes can utilize xanthorhodopsin based proton pumps and bacterial photosynthetic complexes that work in parallel for energy production. They are called dual phototrophic systems. Light sensing requirements in these type of systems are obviously demanding. In nature, the photosensing machinery follows mainly the same composition in all organisms. However, the specific role of each photosensor in specific light conditions is elusive. In this study, we provide an overall picture of photosensors present in dual phototrophic systems. We compare the genomes of the photosensor proteins from dual phototrophs to those from similar microbes with ”single” phototrophicity or microbes without phototrophicity. We find that the dual phototrophic bacteria obtain a larger variety of photosensors than their light inactive counterparts. Their rich domain composition and functional repertoire remains similar across all microbial photosensors. Our study calls further investigations of this particular group of bacteria. This includes protein specific biophysical characterization in vitro, microbiological studies, as well as clarification of the ecological meaning of their host microbial interactions.