RELATION OF CELLULAR ENVELOPES CHARACTERISTICS OF LACTOBACILLUS SPECIES TO THE PRESENCE OR ABSENCE OF S-LAYER PROTEIN

SOFIA ZANINI; MARÍA MERCEDES PALOMINO; MARIANA C. ALLIEVI; JOAQUINA FINA MARTIN; SANDRA M. RUZAL

Ciudad Buenos Aires

Congreso; Reunion Conjunta de Sociedades de Biociencias; 2017

To understand the envelopes organization regarding their relationship with the presence or not of the S-layer protein, we analyzed L. acidophilus, a S-layer bearing species compared to L. casei a non-S-layer-producing species by analyzing sensitivity to peptidoglycan (PG) hydrolytic enzymes, sensitivity to antibiotics with target cell wall (CW) metabolism, microbial adhesion to solvents (MATS) and Electron microscopy (TEM).CW and PG sensitivity to Lysozyme or Mutanolysin are increased in L. acidophilus, being L. casei highly refractory to lyses. Evidence of structural differences in the CW was found by decreased minimal inhibitory concentration (MIC) of hydrolytic enzymes and antibiotics with target PG synthesis for L. acidophilus. This suggested that PG was less cross-linked and/or that fewer layers are present. TEM showed no difference in PG layers thickness although a decrease ratio of thickness to radius is observed for L. acidophilus. This ratio correlates with the decrease yield of CW-SDS extraction for L. acidophilus compared to that obtained from L. casei. For analyzing peptidoglycan composition the fluorophore-assisted carbohydrate electrophoresis (FACE) methods was used and showed that peptidoglycan structure of L acidophilus was less cross-linked than that of L.casei. An increase in hydrophobicity of L. acidophilus was also observed when compared to the highly hydrophilic L. casei. This was related to the protein content, as it was directly decreased after LiCl treatment. The need of the external highly compact of S-layer protein in some species could be a consequence of the fragility of the cell wall, that show difference in the cell-wall structure (PG cross-linking) and envelope components. Studies on other S-layer-containing and non-containing species is the aim of our future work to corroborate the role of the S-layer in maintaining cell wall stability due to the fragility associated with the structure of peptidoglycan layers.