**Acknowledgements**

This work was supported by a grant of the Romanian Ministry of Research and Innovation, CCCDI—UEFISCDI, project number PN-III-P1-1.2-PCCDI-2017- 0476/51-PCCDI/2018, within PNCDI III, ACRONIM: ARHEOCONS.

## **Conflict of interest**

The authors declare no conflict of interest.

## **Thanks**

*Heritage*

deposits.

The identification of bacteria on the surfaces of the analyzed paintings, as the dominant forms and the absence of these in the air samples, denotes the presence of organic materials on the surface of the paintings, which maintain bacterial activity. Most likely, this microbial load came from the previous storage of the art collection in noncompliant spaces and from a layer of dust that favored these

Our observations allow us to ascertain that the exchanges between the painted works and the aeroflora can be favored by the position of the painting in relation to the areas with high tourist traffic, in relation to the distance from the floor and to

Depositing the paintings in a crowded manner in small enclosures with insufficient ventilation, without air conditioning, favors contamination between paintings; thus 8 bacterial and 3 fungal species were identified as being shared among

The identified fungal strains include *Penicillium* sp. and *Aspergillus* sp., which are known in the literature [23] as factors in the deterioration of the layers painted with oil or of the areas of the paintings treated with adhesives. The growth of these hyphae on the support material (canvas) on which the painting is applied favors the

Bacteria associated with painted surfaces can form a characteristic biofilm depending on the age of the painting and the working technique (the nature and

The smaller number of species identified on the canvas (back side) compared to painted surfaces allows important valuations regarding the state of prior preserva-

The presence of colored spores and the production of specific metabolites can produce pigmentation induced by organic acids, which generate major changes in

The instrumental and experimental methods of analyzing the works of art belonging to the sixteenth, seventeenth, eighteenth, and nineteenth centuries, to different schools of painting namely Russian, German, and French, purchased from the art collector Catalin Lazureanu, through ARHEOCONS project and recently exhibited in the "Etta Ionescu" Art Gallery of the Ovidius University of Constanta, hosted by the National Military Museum "King Ferdinand I" in Constanta, have been used to establish the following aspects: attribution to the school or the author, the age of the paintings, the preservation mode, the quality and condition of the painted or support materials, the effects of biological contamination, and the

The original provenance and the previous conservation mode have put their mark on the works of art. Identified species, *Aeromonas* sp., *Corynebacterium* sp., and *Micrococcus* sp., as well as the identification of hemolytic forms suggest contact with the dusty spaces of the deposits. The dust particles can not only act physically or chemically but also be sources of infection of the works of art with fungal spores, bacteria, and insect eggs. Microorganisms can reach the art objects, colonizing them, as they have as source of food the organic particles that enter the components of dust and, are favorable for development in an atmosphere with relatively high

The study allowed new hypotheses on the authenticity of the paintings, to attribute the works to the author or to the school of painting, to identify the

the variations of the conditions of temperature and humidity.

the analyzed paintings, out of a total of 14 isolated morphotypes.

condition of the painted surface, the degree of maintenance, etc.).

friability and the loss of the painted layers.

the painted structure, which cannot be repaired.

tion of the analyzed paintings.

severity of biodegradation.

**3. Conclusions**

**234**

humidity.

Special thanks for consulting to Mr. Costel Coroban.
