Microbial Biofilms at Meat-Processing Plant as Possible Places of Bacteria Survival

Abstract

Biofilm contamination in food production threatens food quality and safety, and causes bacterial infections. Study of food biofilms (BF) is of great importance. The taxonomic composition and structural organization of five foods BF taken in different workshops of a meat-processing plant (Moscow, RF) were studied. Samples were taken from the surface of technological equipment and premises. Metagenomic analysis showed both similarities in the presented microorganisms dominating in different samples, and unique families prevailing on certain objects were noted. The bacteria found belonged to 11 phyla (no archaea). The dominant ones were Actinobacteria, Bacteroidetes, Firmicutes, and Proteobacteria. The greatest diversity was in BFs taken from the cutting table of raw material. Biofilms' bacteria may be the cause of meat, fish and dairy products spoilage possible representatives include Pseudomonas, Flavobacterium, Arcobacter, Vagococcus, Chryseobacterium, Carnobacterium, etc.). Opportunistic human and animal pathogens (possible representatives include Arcobacter, Corynebacterium, Kocuria, etc.) were also found. Electron-microscopic studies of BF thin sections revealed the following: (1) the diversity of cell morphotypes specific to multispecies BFs; (2) morphological similarity of cells in BFs from different samples, micro-colonial growth; (3) age heterogeneity of cells within the same microcolony (vegetative and autolyzed cells, resting forms); (4) heterogeneity of the polymer matrix chemical nature according to ruthenium red staining.

Keywords: foodborne pathogens; meat-processing; microbial biofilm.

Figure 1

Electron micrograph of sample 1 biofilms. Designations: VC I; VC II; VC III, VC IV—vegetative cells of I–IV morphotypes, respectively; P—persisters covered with a fibrillar layer; FL—fibrillar layer; MC—meat cells. Scale bar is 2 μm.

Figure 2

Electron micrograph of sample 1 biofilm (magnified). Designations: P—persisters covered with a fibrillar layer; FL—fibrillar layer; V—vesicle. Scale bar is 0.5 μm.

Figure 3

Electron micrograph of sample 2 biofilm. Designations: VC—vegetative cells; G-VC—vegetative cells of gram-negative bacteria; RF—resting forms; FS—fibrous structures of the matrix; CL—capsular layer; P—persisters; FL—fibrillar layer; A—autolyzed cell. Scale bar is 1 μm.

Figure 4

Electron micrograph of sample 2 biofilm (magnified). Designations: VC—vegetative cells; RF—resting forms; CL—capsular layer; A—autolyzed cell: CN—compacted nucleoid. Scale bar is 0.5 μm.

Figure 5

Electron micrograph of sample 4 biofilm. Designations: VC—vegetative cells; RF—resting forms; CL—capsular layer; I, II, III, IV, V—microcolonies of I–V morphotype cells, respectively; V—vesicles; POBA—polyoxybutyric acid, MC—meat cell. Scale bar is 0.5 μm.

Figure 6

Electron micrographs of sample 5. (A)—zone of BF with veiny material; (B)—zone rich of cells in carbohydrate matrix. Designations: M—matrix (veiny structures VM or carbohydrate structures CS); VC—vegetative cells, and RF—resting forms of the same microcolony; DS—division septum; CL—capsular layer. Scale bar is 0.5 μm.

Figure 7

Taxonomic composition of microbial community of biofilms.

Figure 8

The general of the families found in each samples according to relative abundance. M1, M2, M3, M4 and M5 represent each food processing specific location (x-axis). Color boxes represent bacterial abundance (y-axis).